Using lodash push to an array only if value doesn't exist?
The Set feature introduced by ES6 would do exactly that.
var s = new Set();// Adding aluess.add('hello');s.add('world');s.add('hello'); // already exists// Removing valuess.delete('world');var array = Array.from(s);Or if you want to keep using regular Arrays
function add(array, value) { if (array.indexOf(value) === -1) { array.push(value); }}function remove(array, value) { var index = array.indexOf(value); if (index !== -1) { array.splice(index, 1); }}Using vanilla JS over Lodash is a good practice. It removes a dependency, forces you to understand your code, and often is more performant.
Perhaps _.pull() can help:
var _ = require('lodash');function knock(arr,val){ if(arr.length === _.pull(arr,val).length){ arr.push(val); } return arr;}Mutates the existing array, removes duplicates as well:
> var arr = [1,2,3,4,4,5];> knock(arr,4);[ 1, 2, 3, 5 ]> knock(arr,6);[ 1, 2, 3, 5, 6 ]> knock(arr,6);[ 1, 2, 3, 5 ]