bind.js

/**
 * Basic Implementation
 */
let user = {
  firstName: "John",
};

function testFunc(){
    console.log(this.firstName)
}

// Create a new function 'funcUser' with the 'this' parameter bound to user
let funcUser=testFunc.bind(user);
funcUser(); 
// Output : John

/**
 * Advanced
 */
// Top-level 'this' is bound to 'globalThis' in scripts.
this.x = 9;
const module = {
  x: 81,
  getX() {
    return this.x;
  },
};

// The 'this' parameter of 'getX' is bound to 'module'.
console.log(module.getX()); // 81

const retrieveX = module.getX;
// The 'this' parameter of 'retrieveX' is bound to 'globalThis' in non-strict mode.
console.log(retrieveX()); // 9

// Create a new function 'boundGetX' with the 'this' parameter bound to 'module'.
const boundGetX = retrieveX.bind(module);
console.log(boundGetX()); // 81