What does colon do in JavaScript

Question

I m learning JavaScript and while browsing through the jQuery library I see    colon  being used a lot  What is this used for in JavaScript       Return an array of filtered elements  r     and the modified expression string  t     return   r  r  t  t

User · Accepted Answer

var o         r   some value       t   some other value       is functionally equivalent to  var o   new Object    o r    some value   o t    some other value

User · Answer

The     is a delimiter for key value pairs basically  In your example it is a Javascript Object Literal notation   In javascript  Objects are defined with the colon delimiting the identifier for the property  and its value so you can have the following   return        Property1   125      Property2    something       Method1   function        do nothing           array   5  3  6  7       and then use it like   var o           property1   125      property2    something       method1   function        do nothing           array   5  3  6  7      alert o property1      Will display  125    A subset of this is also known as JSON  Javascript Object Notation  which is useful in AJAX calls because it is compact and quick to parse in server-side languages and Javascript can easily de-serialize a JSON string into an object       The parenthesis      amp      around the object are important here var o   eval         key    value               You can also put the key inside quotes if it contains some sort of special character or spaces  but I wouldn t recommend that because it just makes things harder to work with   Keep in mind that JavaScript Object Literal Notation in the JavaScript language is different from the JSON standard for message passing  The main difference between the 2 is that functions and constructors are not part of the JSON standard  but are allowed in JS object literals

User · Answer

And also  a colon can be used to label a statement  for example  var i   100  j   100  outerloop  while i gt 0      while j gt 0       j       if j gt 50         break outerloop           i

User · Answer

One stupid mistake I did awhile ago that might help some people   Keep in mind that if you are using     in an event like this  the value will not change  var ondrag    function event  ui                                 nub0x  event target offsetLeft   event target clientWidth 2              nub0y   event target offsetTop   event target clientHeight 2                                 So  nub0x  will initialize with the first event that happens and will never change its value  But  nub0y  will change during the next events

User · Answer

That s JSON  or JavaScript Object Notation  It s a quick way of describing an object  or a hash map  The thing before the colon is the property name  and the thing after the colon is its value  So in this example  there s a property  r   whose value is whatever s in the variable r  Same for t

User · Answer

It can be used to list objects in a variable  Also  it is used a little bit in the shorthand of an if sentence   var something    face   hello  man   hey  go   sup      And calling it like this  alert something man     Also the if sentence   function something          some    doathing     dostuff       if some   true doathing     else dostuff

User · Answer

That s JSON  or JavaScript Object Notation  It s a quick way of describing an object  or a hash map  The thing before the colon is the property name  and the thing after the colon is its value  So in this example  there s a property  r   whose value is whatever s in the variable r  Same for t

User · Answer

You guys are forgetting that the colon is also used in the ternary operator  though I don t know if jquery uses it for this purpose    the ternary operator is an expression form  expressions return a value  of an if then statement  it s used like this   var result    condition     value1     value2      A ternary operator could also be used to produce side effects just like if then  but this is profoundly bad practice

User · Answer

The     is a delimiter for key value pairs basically  In your example it is a Javascript Object Literal notation   In javascript  Objects are defined with the colon delimiting the identifier for the property  and its value so you can have the following   return        Property1   125      Property2    something       Method1   function        do nothing           array   5  3  6  7       and then use it like   var o           property1   125      property2    something       method1   function        do nothing           array   5  3  6  7      alert o property1      Will display  125    A subset of this is also known as JSON  Javascript Object Notation  which is useful in AJAX calls because it is compact and quick to parse in server-side languages and Javascript can easily de-serialize a JSON string into an object       The parenthesis      amp      around the object are important here var o   eval         key    value               You can also put the key inside quotes if it contains some sort of special character or spaces  but I wouldn t recommend that because it just makes things harder to work with   Keep in mind that JavaScript Object Literal Notation in the JavaScript language is different from the JSON standard for message passing  The main difference between the 2 is that functions and constructors are not part of the JSON standard  but are allowed in JS object literals

User · Answer

Another usage of colon in JavaScript is to rename a variable  that is  const person          nickNameThatIUseOnStackOverflow   quot schlingel quot       age  30      firstName   quot John quot     let   nickNameThatIUseOnStackOverflow  nick     person     I take nickNameThatIUseOnStackOverflow but want to refer it as  quot nick quot  from now on  nick    quot schling quot    This is useful if you use a third party library that returns values having awkward   long variable names that you want to rename in your code

User · Answer

The     is a delimiter for key value pairs basically  In your example it is a Javascript Object Literal notation   In javascript  Objects are defined with the colon delimiting the identifier for the property  and its value so you can have the following   return        Property1   125      Property2    something       Method1   function        do nothing           array   5  3  6  7       and then use it like   var o           property1   125      property2    something       method1   function        do nothing           array   5  3  6  7      alert o property1      Will display  125    A subset of this is also known as JSON  Javascript Object Notation  which is useful in AJAX calls because it is compact and quick to parse in server-side languages and Javascript can easily de-serialize a JSON string into an object       The parenthesis      amp      around the object are important here var o   eval         key    value               You can also put the key inside quotes if it contains some sort of special character or spaces  but I wouldn t recommend that because it just makes things harder to work with   Keep in mind that JavaScript Object Literal Notation in the JavaScript language is different from the JSON standard for message passing  The main difference between the 2 is that functions and constructors are not part of the JSON standard  but are allowed in JS object literals

User · Answer

It is part of the object literal syntax  The basic format is   var obj     field name   field value   other field  42      Then you can access these values with   obj field name     - gt   field value  obj  field name       - gt   field value    You can even have functions as values  basically giving you the methods of the object   obj  func     function a    return 5   a    obj func 4       - gt  9

User · Answer

Let s not forget the switch statement  where colon is used after each  case

User · Answer

That s JSON  or JavaScript Object Notation  It s a quick way of describing an object  or a hash map  The thing before the colon is the property name  and the thing after the colon is its value  So in this example  there s a property  r   whose value is whatever s in the variable r  Same for t

User · Answer

One stupid mistake I did awhile ago that might help some people   Keep in mind that if you are using     in an event like this  the value will not change  var ondrag    function event  ui                                 nub0x  event target offsetLeft   event target clientWidth 2              nub0y   event target offsetTop   event target clientHeight 2                                 So  nub0x  will initialize with the first event that happens and will never change its value  But  nub0y  will change during the next events

User · Answer

You guys are forgetting that the colon is also used in the ternary operator  though I don t know if jquery uses it for this purpose    the ternary operator is an expression form  expressions return a value  of an if then statement  it s used like this   var result    condition     value1     value2      A ternary operator could also be used to produce side effects just like if then  but this is profoundly bad practice

User · Answer

And also  a colon can be used to label a statement  for example  var i   100  j   100  outerloop  while i gt 0      while j gt 0       j       if j gt 50         break outerloop           i

User · Answer

These are generally the scenarios where colon     is used in JavaScript  1- Declaring and Initializing an Object  var Car    model  2015   color  blue      car object with model and color properties   2- Setting a Label  Not recommended since it results in complicated control structure and Spaghetti code   List   while counter  lt  50         userInput    userInput       counter         if userInput  gt  10000                   break List             3- In Switch Statement  switch  new Date   getDay          case 6          text    Today is Saturday           break       case 0          text    Today is Sunday           break       default           text    Looking forward to the Weekend       4- In Ternary Operator  document getElementById  demo   innerHTML   age gt 18   True     False

User · Answer

These are generally the scenarios where colon     is used in JavaScript  1- Declaring and Initializing an Object  var Car    model  2015   color  blue      car object with model and color properties   2- Setting a Label  Not recommended since it results in complicated control structure and Spaghetti code   List   while counter  lt  50         userInput    userInput       counter         if userInput  gt  10000                   break List             3- In Switch Statement  switch  new Date   getDay          case 6          text    Today is Saturday           break       case 0          text    Today is Sunday           break       default           text    Looking forward to the Weekend       4- In Ternary Operator  document getElementById  demo   innerHTML   age gt 18   True     False

User · Answer

That s JSON  or JavaScript Object Notation  It s a quick way of describing an object  or a hash map  The thing before the colon is the property name  and the thing after the colon is its value  So in this example  there s a property  r   whose value is whatever s in the variable r  Same for t

User · Answer

It is part of the object literal syntax  The basic format is   var obj     field name   field value   other field  42      Then you can access these values with   obj field name     - gt   field value  obj  field name       - gt   field value    You can even have functions as values  basically giving you the methods of the object   obj  func     function a    return 5   a    obj func 4       - gt  9

User · Answer

The     is a delimiter for key value pairs basically  In your example it is a Javascript Object Literal notation   In javascript  Objects are defined with the colon delimiting the identifier for the property  and its value so you can have the following   return        Property1   125      Property2    something       Method1   function        do nothing           array   5  3  6  7       and then use it like   var o           property1   125      property2    something       method1   function        do nothing           array   5  3  6  7      alert o property1      Will display  125    A subset of this is also known as JSON  Javascript Object Notation  which is useful in AJAX calls because it is compact and quick to parse in server-side languages and Javascript can easily de-serialize a JSON string into an object       The parenthesis      amp      around the object are important here var o   eval         key    value               You can also put the key inside quotes if it contains some sort of special character or spaces  but I wouldn t recommend that because it just makes things harder to work with   Keep in mind that JavaScript Object Literal Notation in the JavaScript language is different from the JSON standard for message passing  The main difference between the 2 is that functions and constructors are not part of the JSON standard  but are allowed in JS object literals

User · Answer

It is part of the object literal syntax  The basic format is   var obj     field name   field value   other field  42      Then you can access these values with   obj field name     - gt   field value  obj  field name       - gt   field value    You can even have functions as values  basically giving you the methods of the object   obj  func     function a    return 5   a    obj func 4       - gt  9

User · Answer

You guys are forgetting that the colon is also used in the ternary operator  though I don t know if jquery uses it for this purpose    the ternary operator is an expression form  expressions return a value  of an if then statement  it s used like this   var result    condition     value1     value2      A ternary operator could also be used to produce side effects just like if then  but this is profoundly bad practice

User · Answer

It can be used to list objects in a variable  Also  it is used a little bit in the shorthand of an if sentence   var something    face   hello  man   hey  go   sup      And calling it like this  alert something man     Also the if sentence   function something          some    doathing     dostuff       if some   true doathing     else dostuff

User · Answer

And also  a colon can be used to label a statement  for example  var i   100  j   100  outerloop  while i gt 0      while j gt 0       j       if j gt 50         break outerloop           i

User · Answer

You guys are forgetting that the colon is also used in the ternary operator  though I don t know if jquery uses it for this purpose    the ternary operator is an expression form  expressions return a value  of an if then statement  it s used like this   var result    condition     value1     value2      A ternary operator could also be used to produce side effects just like if then  but this is profoundly bad practice

User · Answer

It is part of the object literal syntax  The basic format is   var obj     field name   field value   other field  42      Then you can access these values with   obj field name     - gt   field value  obj  field name       - gt   field value    You can even have functions as values  basically giving you the methods of the object   obj  func     function a    return 5   a    obj func 4       - gt  9

User · Answer

And also  a colon can be used to label a statement  for example  var i   100  j   100  outerloop  while i gt 0      while j gt 0       j       if j gt 50         break outerloop           i

User · Answer

Let s not forget the switch statement  where colon is used after each  case

User · Answer

Another usage of colon in JavaScript is to rename a variable  that is  const person          nickNameThatIUseOnStackOverflow   quot schlingel quot       age  30      firstName   quot John quot     let   nickNameThatIUseOnStackOverflow  nick     person     I take nickNameThatIUseOnStackOverflow but want to refer it as  quot nick quot  from now on  nick    quot schling quot    This is useful if you use a third party library that returns values having awkward   long variable names that you want to rename in your code

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