I have an array holding a bunch of booleans and a function that adds n new booleans to it. All of them should start with their default value, so one way would be
const array = [];
function extendArrayBy(amountOfNewItems) {
for (let i = 0; i < amountOfNewItems; i++) {
array.push(false);
}
}
extendArrayBy(3);
console.log(array);but there is a Array.prototype.fill() function which might do it "more elegant". What I tried:
let array = [];
const amountOfNewItems = 3;
array = array.fill(false, array.length, array.length + amountOfNewItems);
console.log(array);Unfortunately the modified array does not contain the new items. Does someone know what I missed?
As already said in the comments. fill does not add new elements.
The
fill()method changes all elements in an array to a static value, from a start index (default 0) to an end index (default array.length). It returns the modified array.
You could change the .length before you call fill:
let array = [true, false, true];
const amountOfNewItems = 3;
array.length = array.length + amountOfNewItems
array = array.fill(false, array.length - amountOfNewItems, array.length);
console.log(array);Give this a try:
let amountOfNewItems = 3;
let array = [];
array = array.concat(Array(amountOfNewItems).fill(false));
console.log(array);
let array2 = [1,2,3];
array2 = array2.concat(Array(amountOfNewItems).fill(false));
console.log(array2);Here's a function that extends an array with a given value by a given amount.
let arr = ['A', 1, {k: 'v'}];
/** Extends an array with a given *** value at a given amount.
* @param {Array} array
* @param {Any} element
* @param {Number} size
* @return {Array}
*/
const extend = (array, element, size = 1) => {
let extra = element == undefined ? null : element;
const extArr = [...new Array(size)].map(e => extra);
return [...array, ...extArr];
};
console.log(extend(arr, false, 7));