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Implement Array.forEach

Array.forEach

The forEach() method executes a provided function once for each array element.

Question

Implement the Array.forEach method

Thought process Pseudocode

  1. A function which takes a function as an argument
  2. The function argument must be passed the array index, the item and the context
  3. A check should me made to see if the item exists in the array

Solution

/**
 * Foreach function is attached to the array prototype
 * It takes in a callback and passes every item in the array
 * through the callback
 */
/**
 * The callback gets 3 arguments
 * the item, the index and the  execution context
 * A for each array loop cannot be broken using break;
 */
Array.prototype.newForEach = function (callback, context) {
  for (let index = 0; index < this.length; index++) {
    // This is primarily to check if the item
    // exists in the array, 
    if (this.indexOf(this[index]) > -1) {
      callback.call(context, this[index], index, this)
    }
  }
}
// example
const words = ["adam", "ate", "an", "apple"]
const upperCaseList = []
words.newForEach((word, index, context) => {
  upperCaseList.push(word.toUpperCase())
})
console.log(upperCaseList)

Caveat

The for each loop cannot be broken, in between. In such case where the loop must be exited when a condition is met, Array.some or Array.find me be a better option.