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Flatten an array in JavaScript.
We are required to write a JavaScript array function that takes in a nested array and returns an array with all the elements present in the array without any nesting.
For example −
//if the input is: const arr = [[1, 2, 3], [4, 5], [6]]; //then the output should be: const output = [1, 2, 3, 4, 5, 6];
Therefore, let’s write the code for this function −
Method 1: Using recursion
Here we will loop over the original nested array and recursively push the nested element elements into a new array.
Example
const arr = [[1, 2, 3], [4, 5], [6]];
const flatten = function(){
let res = [];
for(let i = 0; i < this.length; i++){
if(Array.isArray(this[i])){
res.push(...this[i].flatten());
} else {
res.push(this[i]);
};
};
return res;
};
Array.prototype.flatten = flatten;
console.log(arr.flatten());Method 2: Using Arrray.prototype.reduce()
Here we will use the reduce() method to construct a new array like this −
Example
const arr = [[1, 2, 3], [4, 5], [6]];
const flatten = function(){
return this.reduce((acc, val) => {
return acc.concat(...val);
}, []);
};
Array.prototype.flatten = flatten;
console.log(arr.flatten());Output
The console output for both of the methods will be −
[ 1, 2, 3, 4, 5, 6 ]
Updated on: 25-Aug-2020
190 Views
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