Summarize several methods of traversing arrays in JavaScript

This article summarizes some methods for traversing arrays in javascript. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

There are several ways to traverse an array, and they will be listed one by one below!

while loop

let index = 0;
const array = [1, 2, 3, 4, 5];

while (index < array.length) {
    console.log(array[index]);
    index++;
}

for loop

const array = [1,2,3,4,5];
for(let index=0;index<array.length;index++){
    console.log(array[index]);
}
for(let index in array){
    console.log(array[index]);
}

forEach

const array=[1,2,3,4,5];
array.forEach(function(current_value,index,array){
    console.log(`At index ${index} in array ${array} the value is ${current_value}`)
})

map

The last construct is useful, but does not return a new array, which may be undesirable for your particular case. map solves this problem by applying a function to each element and then returning a new array.

const array = [1,2,3,4,5];
const square = x =>Math.pow(x,2);
const squares = array.map(square);
console.log(`${array}`);
console.log(`${squares}`)

reduce

The reduce() method applies a function to the accumulator and each element in the array (from left to right) to Reduce to a single value

const array = [1,2,3,4,5];
const sum = (x,y) => x + y;

const array_sum = array.reduce(sum,0);
console.log(`the sum of arrray:${array} is ${array_sum}`);

filter

Filter elements in the array based on a Boolean function

const array = [1,2,3,4,5];
const even = x => x%2 === 0;
const even_array = array.filter(even);
console.log(`even numbers in array ${array} : ${even_array}`);

every

I got an array and wanted to test whether each element meets the given condition

const array = [1,2,3,4,5,8];
const under_six = x => x<6;
if(array.every(under_six)){
    console.log(`every elemnet in the array is less than 6`);
}
else{
    console.log(`at least one element in the array was bigger than 6`);
}

some

Test whether At least one element matches the Boolean function

const array = [2,4,5,6,8];
const over_five = x => x>5;

if(array.some(over_five)){
    console.log(`at least one element bigger than 5 was found`);
}
else{
    console.log(`no element bigger than 5 was found`);
}

That’s it. If you have anything else, please add it!

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