Function prototype – JavaScript Challenges

You can find all the code in this post at repo Github.

Function prototype related challenges

Function.prototype.call()

/**
* @param {any} thisArg
* @param {…*} argArray
* @return {any}
*/

Function.prototype.myCall…


This content originally appeared on DEV Community and was authored by Mitchell

You can find all the code in this post at repo Github.

Function prototype related challenges

Function.prototype.call() 

/**
 * @param {any} thisArg
 * @param {...*} argArray
 * @return {any}
 */

Function.prototype.myCall = function (thisArg, ...argArray) {
  const sym = Symbol();
  const wrapperObj = Object(thisArg);

  Object.defineProperty(wrapperObj, sym, {
    enumerable: false,
    value: this,
  });

  return wrapperObj[sym](...argArray);
};

// Usage example
function multiplyAge(multiplier = 1) {
  return this.age * multiplier;
}

const mary = {
  age: 21,
};

const john = {
  age: 42,
};

console.log(multiplyAge.myCall(mary)); // 21
console.log(multiplyAge.myCall(john, 2)); // 84

Function.prototype.apply() 

/**
 * @param thisArg The object to be used as the this object.
 * @param argArray A set of arguments to be passed to the function.
 * @return {any}
 */

Function.prototype.myApply = function (thisArg, argArray = []) {
  const sym = Symbol();
  const wrapperObj = Object(thisArg);

  Object.defineProperty(wrapperObj, sym, {
    enumerable: false,
    value: this,
  });

  return wrapperObj[sym](...argArray);
};

// Usage example
function multiplyAge(multiplier = 1) {
  return this.age * multiplier;
}

const mary = {
  age: 21,
};

const john = {
  age: 42,
};

console.log(multiplyAge.myApply(mary)); // 21
console.log(multiplyAge.myApply(john, [2])); // 84

Function.prototype.bind() 

/**
 * @param {any} thisArg
 * @param {...*} argArray
 * @return {Function}
 */

Function.prototype.myBind = function (thisArg, ...argArray) {
  const sym = Symbol();
  const wrapperObj = Object(thisArg);

  Object.defineProperty(wrapperObj, sym, {
    enumerable: false,
    value: this,
  });

  return function (...args) {
    return wrapperObj[sym](...argArray, ...args);
  };
};

// Usage example
const john = {
  age: 42,
  getAge: function () {
    return this.age;
  },
};

const unboundGetAge = john.getAge;
console.log(unboundGetAge()); // undefined

const boundGetAge = john.getAge.myBind(john);
console.log(boundGetAge()); // 42

const jack = {
  age: 21,
  getAge: function () {
    return this.age;
  },
};

// For multiple `.bind()` chaining, only the first one would work
const boundJohnGetAge = john.getAge.myBind(john).myBind(jack);
console.log(boundGetAge()); // 42

Reference


This content originally appeared on DEV Community and was authored by Mitchell


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Mitchell | Sciencx (2024-11-01T03:59:56+00:00) Function prototype – JavaScript Challenges. Retrieved from https://www.scien.cx/2024/11/01/function-prototype-javascript-challenges/

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