javascript之querySelector和querySelectorAll使用介绍

(function(global) { 
global.doc = document; 
global.body = doc.getElementsByTagName('body')[0]; 
global.$ = function(id) { 
return doc.getElementById(id); 
} 
global.Logger = function(id) { 
this.logElem = $(id); 
this.logArr = []; 
}; 
global.Logger.prototype = { 
constructor: global.logger, 
append: function(comment) { 
this.logArr.push('
' + comment + '
'); 
}, 
flush: function() { 
this.logElem.innerHTML = this.logArr.join(''); 
}, 
clear: function() { 
this.logElem.innerHTML = ''; 
this.logArr = []; 
} 
}; 
})(this); 
(function() { 
var logger = new Logger('log'); 
var items = $('inner').querySelectorAll('#main h4.inside'); 
logger.append(items.length); 
for(var i = 0, len = items.length; i ' + comment + '
'); 
}, 
flush: function() { 
this.logElem.innerHTML = this.logArr.join(''); 
}, 
clear: function() { 
this.logElem.innerHTML = ''; 
this.logArr = []; 
} 
}; 
})(this); 
(function() { 
var logger = new Logger('log'); 
var items = $('inner').querySelectorAll('#main h4.inside'); 
logger.append(items.length); 
for(var i = 0, len = items.length; i 

 
 
h4 inside 1
 
h4 inside 2
 
 
list item one
 
list item two
 
list itme three
 
 
 
 
h4 outside 1
 
h4 outside 2
 
 

#log { 
font-size: 10px; 
}