How do I check whether an array contains a string in TypeScript

Question

Currently I am using Angular 2 0  I have an array as follows   var channelArray  Array lt string gt      one    two    three      How can I check in TypeScript whether the channelArray contains a string  three

User · Answer

TS has many utility methods for arrays which are available via the prototype of Arrays. There are multiple which can achieve this goal but the two most convenient for this purpose are:

Array.indexOf() Takes any value as an argument and then returns the first index at which a given element can be found in the array, or -1 if it is not present.
Array.includes() Takes any value as an argument and then determines whether an array includes a this value. The method returning true if the value is found, otherwise false.

Example:

const channelArray: string[] = ['one', 'two', 'three'];

console.log(channelArray.indexOf('three'));      // 2
console.log(channelArray.indexOf('three') > -1); // true
console.log(channelArray.indexOf('four') > -1);  // false
console.log(channelArray.includes('three'));     // true

User · Answer

Use JavaScript Array includes   Method  var fruits     Banana    Orange    Apple    Mango    var n   fruits includes  Mango      Try it Yourself    link  Definition  The includes   method determines whether an array contains a specified element   This method returns true if the array contains the element  and false if not

User · Answer

Also note that  in  keyword  does not work on arrays  It works on objects only     propName in myObject   Array inclusion test is   myArray includes  three

User · Answer

If your code is ES7 based  or upper versions   channelArray includes  three      will return true or false  If not  for example you are using IE with no babel transpile  channelArray indexOf  three       -1    will return true or false  the indexOf method will return the position the element has into the array  because of that we use     different from -1 if the needle is found at the first position

User · Answer

do like this   departments  string       if this departments indexOf this departmentName trim     gt -1                return

User · Answer

You can use the some method   console log channelArray some x   gt  x      three        true   You can use the find method   console log channelArray find x   gt  x      three        three   Or you can use the indexOf method   console log channelArray indexOf  three        2

User · Answer

You can use filter too    this products   array products filter  x    gt  x Name includes  ABC

User · Answer

The same as in JavaScript  using Array prototype indexOf     console log channelArray indexOf  three    gt  -1     Or using ECMAScript 2016 Array prototype includes     console log channelArray includes  three         Note that you could also use methods like showed by  Nitzan to find a string  However you wouldn t usually do that for a string array  but rather for an array of objects  There those methods were more sensible  For example  const arr     foo   bar     foo   bar     foo   baz     console log arr find e   gt  e foo      bar         foo   bar    first match  console log arr some e   gt  e foo      bar        true console log arr filter e   gt  e foo      bar          foo   bar     foo   bar      Reference   Array find    Array some    Array filter

[javascript] How do I check whether an array contains a string in TypeScript?

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