Why is (function(){return this}).bind('abc')()==='abc' equals to false?

Question

Suppose I have a function like that:

var f1=function(){
   return this;
};
console.log(f1.bind('abc')()==='abc');

as I know, f1.bind('abc') should create a new function that returns 'abc', so I guess it should have output same as

console.log('abc'==='abc')

which is true, but now the output is false, what's wrong with my guess?

Answer 1

In non-strict mode, the primitive values are wrapped in Object. So, 'abc' becomes new Object('abc').

In strict mode, this does not happen.

'use strict';

var f1 = function() {
  return this;
};
console.log(f1.bind('abc')() === 'abc');

Quoting from ES6 Specifications for strict mode

If this is evaluated within strict mode code, then the this value is not coerced to an object. A this value of null or undefined is not converted to the global object and primitive values are not converted to wrapper objects. The this value passed via a function call (including calls made using Function.prototype.apply and Function.prototype.call) do not coerce the passed this value to an object (9.2.1.2, 19.2.3.1, 19.2.3.3).