#How to #JS #ES6 #Arrays

The concat method

With concat, we do not have to add even a single for...in loop. Instead, we can simply chain the concat method in the order we want!

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const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
const array3 = [7, 8, 9];

const mergedArray = []
  .concat(array1)
  .concat(array2)
  .concat(array3);

console.log(mergedArray); // [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

Tip: Prefer starting with empty array when chaining concat. In this way, it is clear that we make a new array and do not manipulate the existing ones! ^_^

Spread Operator (Since ES6)

With ES6 it is simple now! We can merge two or more arrays in one line:

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const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
const array3 = [7, 8, 9];

const mergedArray = [...array1, ...array2, ...array3];

console.log(mergedArray); // [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
#How to #JS #ES6 #Arrays