function $(selector){
// Get the first character
var firstLetter = selector.charAt(0);
// The first character of judge
switch(firstLetter){
// # id name was;
case '#' : return idSelector(selector);
break;
// was class;
case '.' : return classSelector(selector);
break;
default : return tagNameSelector(selector);
}
//idSelector
function idSelector(idS){
return document.getElementById(idS.substring(1));
}
//tagNameSelector;
function tagNameSelector(tagNameS){
return document.getElementsByTagName(tagNameS);
}
//classSelector
function classSelector(classS){
// compatible processing
if(docuent.getElementsByClassName){
return document.getElementsByClassName(classS.substring(1));
}else{
// array placed dom node
was arr = [];
// If the browser is not compatible getElementsByClassName
// get all elements on the page
var arrTag = document.getElementsByTagName('*');
// use regular matches to find the corresponding label
var reg = new RegExp('(^|\\s)'+classS.substring(1)+'($|\\s)','g');
// loop through all of the labels
for(var i = 0 , k = arrTag.length ; i < k ; i++){
// If the label has the name of the class with a push into an array
console.log(arrTag[i].className);
if(reg.test(arrTag[i].className)){
arr.push(arrTag[i]);
}
}
return arr;
}
}
}