javascript code to loop through array code example

Example 1: javascript loop through array

var data = [1, 2, 3, 4, 5, 6];

// traditional for loop
for(let i=0; i<=data.length; i++) {
  console.log(data[i])  // 1 2 3 4 5 6
}

// using for...of
for(let i of data) {
	console.log(i) // 1 2 3 4 5 6
}

// using for...in
for(let i in data) {
  	console.log(i) // Prints indices for array elements
	console.log(data[i]) // 1 2 3 4 5 6
}

// using forEach
data.forEach((i) => {
  console.log(i) // 1 2 3 4 5 6
})
// NOTE ->  forEach method is about 95% slower than the traditional for loop

// using map
data.map((i) => {
  console.log(i) // 1 2 3 4 5 6
})

Example 2: javascript code to loop through array

var colors = ["red","blue","green"];
for (var i = 0; i < colors.length; i++) {
    console.log(colors[i]);
}

Example 3: loop an array in javascript

let array = ["loop", "this", "array"]; // input array variable
for (let i = 0; i < array.length; i++) { // iteration over input
	console.log(array[i]); // logs the elements from the current input
}

Example 4: iterate through array javascript

var myStringArray = ["Hello","World"];
var arrayLength = myStringArray.length;
for (var i = 0; i < arrayLength; i++) {
    console.log(myStringArray[i]);
    //Do something
}

Example 5: javascript loop through array

let my_array = [1, 2, 3, 4, 5];

// standard for loop
for(let i = 0; i < my_array.length; i++) {
  console.log(my_array[i])  // 1 2 3 4 5 6
}

// for and of method
for(let i of my_array) {
	console.log(i)
}

/*
Results:
1 2 3 4 5
1 2 3 4 5
(From both methods)
*/

Example 6: javascript loop through array

array iteration styles illustrate programming paradigms
let newArray = [];  const theArray = [2, 4, 6, 8, 10]
// 1) imperative, explicit
for (var i = 0; i < theArray.length; i++) {  // var is mutable
    console.log(theArray[i]);                // side effect from writing to console
	newArray[i] = theArray[i] * theArray[i]  // let is mutable
}
// 2) forEach function of the Array class TIP: console.log(Array) //Does not change the array, Returns undefined
function f1(theValue, theIndex, originalArray) { numVal = numVal *  theValue }
theArray.forEach(f1);   console.log( ` creates  ${   newArray   }` );
run.addEventListener("click", function () {cpeople.forEach((element) => console.log(element.firstname));});
// 3) declarative, implicit 
function f1(v,i,a) { v=v*v }
const constArray = theArray.map(fNumbers); 
console.log( ` immutable  ${ newArray }` );