preload.js

var imgSrcArr = ['blue', 'pink', 'red', 'orange', 'purple', 'gold'];

var imgWrap = [];

function preloadImg(arr) {
    for (var i = 0; i < arr.length; i++) {
        for (var j = 0; j <= 25; j++) {
            var wrapI = i * 26 + j;
            imgWrap[wrapI] = new Image();

            imgWrap[wrapI].src = './images/' + arr[i] + '/' + j + '.png';
        }
    }
}

var imgSrcArr2 = ['blue2', 'blue3', 'green', 'yellow'];
var imgWrap2 = [];
function preloadImg2(arr) {
    for (var i = 0; i < arr.length; i++) {
        for (var j = 0; j <= 11; j++) {
            var wrapI = i * 11 + j;
            imgWrap2[wrapI] = new Image();

            imgWrap2[wrapI].src = './images/points/' + arr[i] + '/' + j + '.png';
        }
    }
}