React Native Cookbook - Second Edition

How to do it...

1. The first optimization to look at is speeding up iterations. Often, you'll likely be using functions that take iterator functions as arguments (forEach, filter, and map). As a rule of thumb, these will be slower than doing a standard for loop. If the size of the collection you're iterating over is very large, this could make a difference. Here's an example of a faster filter function:

let myArray = [1,2,3,4,5,6,7];let newArray;// Slower: function filterFn(element) {   return element > 2; } newArray = myArray.filter(filterFn); // Faster: function filterArray(array) {   var length = array.length,     myNewArray = [],     element,     i;    for(i = 0; i < length; i++) {     element = array[i];     if(element > 2) {  myNewArray.push(array[i]); ...