代码高亮的功能

//这是JS代码示例，使用自动主题
function selectText() {
        var range,
            selection;

        if (isOS()) {
            range = document.createRange();
            range.selectNodeContents(textArea);
            selection = window.getSelection();
            selection.removeAllRanges();
            selection.addRange(range);
            textArea.setSelectionRange(0, 999999);
        } else {
            textArea.select();
        }
    }