<pre class="shiki github-dark shaku"><code>// CALL POLYFILL// args is arguments one by oneFunction.prototype.mycall = function(context, ...args) { // you tie a function into an object(context) as if it belonged to the object const symbol = Symbol(); // create unique key context = Object(context || window); // set context to windows if null and Create an object to handle primitive values // 'this' points to the calling function here context[symbol] = this; // assign the function to a unique method created on the context const result = context[symbol](...args); // call the function delete context[symbol]; // delete the unique key return result; // return result}// BIND POLYFILL// bind returns a func which when called behave like apply, callFunction.prototype.mybind = function(context, ...args) { const symbol = Symbol(); context[symbol] = this; return function(){ const result = context[symbol](...args); // call the function delete context[symbol]; // delete the unique key return result; // return result }}// APPLY POLYFILL// code exact same as call just the args is an array here so need to destruct(...)Function.prototype.myapply = function(context, args) { // you tie a function into an object(context) as if it belonged to the object const symbol = Symbol(); // create unique key context = Object(context || window); // set context to windows if null and Create an object to handle primitive values // 'this' points to the calling function here context[symbol] = this; // assign the function to a unique method created on the context const result = context[symbol](...args); // call the function delete context[symbol]; // delete the unique key return result; // return result}// Testinglet obj = { a: 10, b: 20}function tester(a, b){ return `a: ${this.a} and b: ${this.b} | curr args a: ${a} and b: ${b}`;}console.log(tester.mycall(obj, 30, 40));const bindFunc = tester.mybind(obj, 30, 40);console.log(bindFunc());console.log(tester.myapply(obj, [30, 40]));</code></pre>

Polyfill for all --- Call, Bind, Apply

Function.prototype.call is very useful when we want to alter the this of a function. Can you implement your own myCall, which returns the same result …