How do I pass the this context to a function

Question

I thought this would be something I could easily google  but maybe I m not asking the right question     How do I set whatever  this  refers to in a given javascript function   for example  like with most of jQuery s functions such as       selector  each function            this  gives me access to whatever selector we re on       How do I write call my own standalone functions that have an appropriate  this  reference when called   I use jQuery  so if there s a jQuery-specific way of doing it  that d be ideal

User · Answer

Another basic example   NOT working   var img   new Image  img onload   function        this myGlobalFunction img      img src   reader result    Working   var img   new Image  img onload   function        this myGlobalFunction img     bind this   img src   reader result    So basically  just add  bind this  to your function

User · Answer

Javascripts  call   and  apply   methods allow you to set the context for a function   var myfunc   function        alert this name       var obj a         name    FOO      var obj b         name    BAR         Now you can call   myfunc call obj a     Which would alert FOO  The other way around  passing obj b would alert BAR    The difference between  call   and  apply   is that  call   takes a comma separated list if you re passing arguments to your function and  apply   needs an array   myfunc call obj a  1  2  3   myfunc apply obj a   1  2  3      Therefore  you can easily write a function hook by using the apply   method  For instance  we want to add a feature to jQuerys  css   method  We can store the original function reference  overwrite the function with custom code and call the stored function   var  css     fn css    fn css   function       alert  hooked         css apply this  arguments        Since the magic arguments object is an array like object  we can just pass it to apply    That way we guarantee  that all parameters are passed through to the original function

User · Answer

You can use the bind function to set the context of this within a function   function myFunc       console log this str    const myContext    str   my context   const boundFunc   myFunc bind myContext   boundFunc        my context

User · Answer

jQuery uses a  call      method to assign the current node to this inside the function you pass as the parameter   EDIT   Don t be afraid to look inside jQuery s code when you have a doubt  it s all in clear and well documented Javascript   ie  the answer to this question is around line 574  callback call  object  name    name  object  name         false

User · Answer

Use function call   var f   function      console log this     f call that  arg1  arg2  etc     Where that is the object which you want this in the function to be

[javascript] How do I pass the this context to a function?

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