In ES6 using Array from() and keys() methods. Array.from(Array(10).keys()) //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Shorter version using spread operator. […Array(10).keys()] //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Start from 1 by passing map function to Array from(), with an object with a length property: Array.from({length: … Read more
Use the find() method: myArray.find(x => x.id === ’45’).foo; From MDN: The find() method returns the first value in the array, if an element in the array satisfies the provided testing function. Otherwise undefined is returned. If you want to find its index instead, use findIndex(): myArray.findIndex(x => x.id === ’45’); From MDN: The findIndex() … Read more
There are several ways of checking if an variable is an array or not. The best solution is the one you have chosen. variable.constructor === Array This is the fastest method on Chrome, and most likely all other browsers. All arrays are objects, so checking the constructor property is a fast process for JavaScript engines. … Read more
The reason is that one construct: var a = []; // Create a new empty array. a[5] = 5; // Perfectly legal JavaScript that resizes the array. for (var i = 0; i < a.length; i++) { // Iterate over numeric indexes from 0 to 5, as everyone expects. console.log(a[i]); } /* Will display: undefined … Read more
You can use it like this: ## declare an array variable declare -a arr=(“element1” “element2” “element3”) ## now loop through the above array for i in “${arr[@]}” do echo “$i” # or do whatever with individual element of the array done # You can access them using echo “${arr[0]}”, “${arr[1]}” also Also works for multi-line … Read more
Use this: let oldArray = [1, 2, 3, 4, 5]; let newArray = oldArray.slice(); console.log({newArray}); Basically, the slice() operation clones the array and returns a reference to a new array. Also note that: For references, strings and numbers (and not the actual object), slice() copies object references into the new array. Both the original and … Read more
There’s no built-in ability to break in forEach. To interrupt execution you would have to throw an exception of some sort. eg. var BreakException = {}; try { [1, 2, 3].forEach(function(el) { console.log(el); if (el === 2) throw BreakException; }); } catch (e) { if (e !== BreakException) throw e; } JavaScript exceptions aren’t terribly … Read more
Use unshift. It’s like push, except it adds elements to the beginning of the array instead of the end. unshift/push – add an element to the beginning/end of an array shift/pop – remove and return the first/last element of an array A simple diagram… unshift -> [array] <- push shift <- [array] -> pop and … Read more
TL;DR Using the Set constructor and the spread syntax: uniq = […new Set(array)]; “Smart” but naïve way uniqueArray = a.filter(function(item, pos) { return a.indexOf(item) == pos; }) Basically, we iterate over the array and, for each element, check if the first position of this element in the array is equal to the current position. Obviously, … Read more
Ways to clear an existing array A: Method 1 (this was my original answer to the question) A = []; This code will set the variable A to a new empty array. This is perfect if you don’t have references to the original array A anywhere else because this actually creates a brand new (empty) … Read more