JS_DOM_Shim

var button = document.getElementById('execute');
var button1 = document.getElementById('execute1');

button.onclick = execute;
button1.onclick = execute1;

function execute() {
    (function() {
        if (!document.querySelector) {
            document.querySelector = function(selector) {
                switch (selector.charAt(0)) {
                    case '#':
                        return document.getElementById(selector.substring(1));
                        break;
                    case '.':
                        return document.getElementsByClassName(selector.substring(1))[0];
                        break;
                    default:
                        return document.getElementsByTagName(selector)[0];
                        break;
                }
            }
        }

    }());

    var wrapper = document.querySelector('#wrapper');
    wrapper.style.background = 'blue';
}

function execute1() {
    (function check() {
        if (!document.querySelectorAll) {
            document.querySelectorAll = function(selector) {
                switch (selector.charAt(0)) {
                    case '#':
                        return document.getElementById(selector.substring(1));
                        break;
                    case '.':
                        return document.getElementsByClassName(selector.substring(1));
                        break;
                    default:
                        return document.getElementsByTagName(selector);
                        break;
                }
            }
        }
    }());

    var divs = document.querySelectorAll('.innerDiv');

    for (var i = 0; i < divs.length; i++) {
        divs[i].style.background = 'pink';
    };
}

//Here we implement the method getElementsByClassName because it is not supported on IE8
document.getElementsByClassName = function(cl) {
    var retnode = [];
    var elem = this.getElementsByTagName('*');
    for (var i = 0; i < elem.length; i++) {
        if ((' ' + elem[i].className + ' ').indexOf(' ' + cl + ' ') > -1) retnode.push(elem[i]);
    }
    return retnode;
};