在上篇介绍了选择器的获取标签、id、类名的方法，现在我们在上篇基础上继续升级
1、问题描述：上篇get（'选择器'）已经实现，如果get方法里是一个选择器的父元素，父元素是DOM对象，那么如何获取元素
思路：1、首先想到的是标签、id、类名的三个方法 2、假设是body节点，那么方法中的document改成body 3、传入的参数如何判断是否为DOM
注意：在获取id方法中全局也只有一个id，所以其中的doument无须修改
修改如下
// 注释: 对获取DOM对象方法的封装
var getTag = function ( tag, context, results ) {
results = results || [];
context = context || document;//防止context是空时报错现象出现 results.push.apply( results, context.getElementsByTagName( tag ) );
return results;
}; var getId = function ( id, results ) {
results = results || [];
results.push( document.getElementById( id ) );
return results;
}; var getClass = function ( className, context, results ) {
results = results || [];
context = context || document;
if ( document.getElementsByClassName ) {
results.push.apply( results, context.getElementsByClassName( className ) );
} else {
each( getTag( '*', context ), function ( i, v ) {
if ( ( ' ' + v.className + ' ' )
.indexOf( ' ' + className + ' ' ) != -1 ) {
results.push( v );
}
} );
}
return results;
}; // 对each方法的封装
var each = function ( arr, fn ) {
for ( var i = 0; i < arr.length; i++ ) {
if ( fn.call( arr[ i ], i, arr[ i ] ) === false ) {
break;
}
}
}; // 通用的get方法
var get = function ( selector, context, results ) {
results = results || [];
var rquickExpr = /^(?:#([\w-]+)|\.([\w-]+)|([\w]+)|(\*))$/,
m = rquickExpr.exec( selector ); if ( m ) {
if ( m[ 1 ] ) {
results = getId( m[ 1 ], results );
} else if ( m[ 2 ] ) {
results = getClass( m[ 2 ], context, results );
} else if ( m[ 3 ] ) {
results = getTag( m[ 3 ], context, results );
} else if ( m[ 4 ] ) {
results = getTag( m[ 4 ], context, results );
} }
验证以上封装的方法，html如下（为了使用方便，以下封装的js都单独放在common.js文件中，在html中须引入使用）
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.rect {
width: 400px;
height: 50px;
margin: 10px 0;
}
.c { border: 1px dashed red; }
.c1 { border: 1px dashed green; }
.c2 { border: 1px dashed blue; }
</style>
<script src="common.js"></script>//把上面的函数单独放在一个js文件中，在html中引入
</head>
<body>
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
<hr />
<div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
</body>
<script type="text/javascript">
get( '.c1', get( '.c' )[ 0 ] )[ 1]
.style.backgroundColor = 'lightgreen'; </script>
</html>
2、问题描述：假设get方法中传入的context是一个DOM数组
思路：首先想到需要遍历数组，那么问题来了，如何判断是否为DOM数组，如果不是数组怎么办，还有在哪一个方法中遍历呢
// 注释: 对基本DOM数组方法的封装
var getTag = function ( tag, context, results ) {
results = results || [];
results.push.apply( results, context.getElementsByTagName( tag ) );
return results;
}; var getId = function ( id, results ) {
results = results || [];
results.push( document.getElementById( id ) );
return results;
}; var getClass = function ( className, context, results ) {
results = results || []; if ( document.getElementsByClassName ) {
results.push.apply( results, context.getElementsByClassName( className ) );
} else {
each( getTag( '*', context ), function ( i, v ) {
if ( ( ' ' + v.className + ' ' )
.indexOf( ' ' + className + ' ' ) != -1 ) {
results.push( v );
}
} );
}
return results;
}; // 对each方法的封装
var each = function ( arr, fn ) {
for ( var i = 0; i < arr.length; i++ ) {
if ( fn.call( arr[ i ], i, arr[ i ] ) === false ) {
break;
}
}
}; // 通用的方法
var get = function ( selector, context, results ) {
results = results || [];
context = context || document;
// 1 2 3 4
var rquickExpr = /^(?:#([\w-]+)|\.([\w-]+)|([\w]+)|(\*))$/,
m = rquickExpr.exec( selector ); if ( m ) {
//此处判断context是否为数组，如果不是数组让其成为数组
if ( context.nodeType ) {
context = [ context ];
}
each( context, function ( i, v ) {
if ( m[ 1 ] ) {
results = getId( m[ 1 ], results );
} else if ( m[ 2 ] ) {
results = getClass( m[ 2 ], this, results );//this可以替代v
} else if ( m[ 3 ] ) {
results = getTag( m[ 3 ], this, results );
} else if ( m[ 4 ] ) {
results = getTag( m[ 4 ], this, results );
}
} );
} return results;
};
验证以上封装的方法，html如下
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.rect {
width: 400px;
height: 50px;
margin: 10px 0;
}
.c { border: 1px dashed red; }
.c1 { border: 1px dashed green; }
.c2 { border: 1px dashed blue; }
</style>
<script src="common.js"></script>
</head>
<body>
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
<hr />
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
</body>
<script type="text/javascript">
var l = get( '.c' );
each( get( '.c1', l ), function () {
this.style.backgroundColor = 'lightblue';
} );
</script>
</html>
3、问题描述：假设get方法中传入的context是一个选择器字符串，也就是在页面中找到一个节点，然后在其后代再找出符合要求的节点
思路：此时传入context是一个选择器字符串，判断其是否为字符串，现在假设先把这个字符串找出来，然后再通过each方法找出其后代的元素
var myPush = function( target, els ) {
var j = target.length,
i = 0;
// Can't trust NodeList.length
while ( (target[j++] = els[i++]) ) {}
target.length = j - 1;
};
// 注释: 对基本方法的封装
var getTag = function ( tag, context, results ) {
results = results || [];
//此处也无须用context=context||[]
try {
results.push.apply( results, context.getElementsByTagName( tag ) );//ie8及以下版本不支持传入伪数组
} catch ( e ) {
myPush( results, context.getElementsByTagName( tag ) );//对ie8及以下版本的支持
}
return results;
};
var getId = function ( id, results ) {
results = results || [];
results.push( document.getElementById( id ) );
return results;
};
var getClass = function ( className, context, results ) {
results = results || [];
if ( document.getElementsByClassName ) {
results.push.apply( results, context.getElementsByClassName( className ) );
} else {
each( getTag( '*', context ), function ( i, v ) {
if ( ( ' ' + v.className + ' ' )
.indexOf( ' ' + className + ' ' ) != -1 ) {
results.push( v );
}
} );
}
return results;
};
// 对each方法的封装
var each = function ( arr, fn ) {
for ( var i = 0; i < arr.length; i++ ) {
if ( fn.call( arr[ i ], i, arr[ i ] ) === false ) {
break;
}
}
};
// 通用的get方法
var get = function ( selector, context, results ) {
results = results || [];
context = context || document;
var rquickExpr = /^(?:#([\w-]+)|\.([\w-]+)|([\w]+)|(\*))$/,
m = rquickExpr.exec( selector );
if ( m ) {
if ( context.nodeType ) {
context = [ context ];
}
//此时对context判断是否为字符串，如果是假设已经找出context
if ( typeof context == 'string' ) {
context = get( context );
}
each( context, function ( i, v ) {
if ( m[ 1 ] ) {
results = getId( m[ 1 ], results );
} else if ( m[ 2 ] ) {
results = getClass( m[ 2 ], this, results );//此处可以用this，也可以用v
} else if ( m[ 3 ] ) {
results = getTag( m[ 3 ], this, results );
} else if ( m[ 4 ] ) {
results = getTag( m[ 4 ], this, results );
}
} );
}
return results;
};
验证以上封装的方法，html如下
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.rect {
width: 400px;
height: 50px;
margin: 10px 0;
}
.c {
border: 1px dashed red;
}
.c1 { border: 1px dashed green; }
.c2 { border: 1px dashed blue; }
</style> <script src="common.js"></script>
</head>
<body>
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
<hr />
<div>
<div class="c1 rect"></div>
<div class="c2 rect"></div>
</div>
<hr />
<div class="c">
<div class="c1 rect"></div>
</div>
</body>
<script type="text/javascript">
// 在页面中找到所有的 .c 的节点, 然后在 .c 的后代元素中
// 找符合 .c1 的节点, 并返回
each( get( '.c1', '.c' ), function () {
this.style.backgroundColor = 'skyblue';
} );
</script>
</html>
4、问题描述：假设get方法中传入的context是多个选择器字符串，在这处理的是组合选择器
思路： 拿到多个选择器的字符串, 首先需要处理的是逗号，将其分解成几个简单的部分, 然后再逐一处理，每一个子选择器, 都是按照从左往右的形式去过滤，先处理一个选择器, 得到的结果再被后面的选择器进行处理
var myPush = function( target, els ) {
var j = target.length,
i = 0;
// Can't trust NodeList.length
while ( (target[j++] = els[i++]) ) {}
target.length = j - 1;
};
// 注释: 对基本方法的封装
var getTag = function ( tag, context, results ) {
results = results || [];
try {
results.push.apply( results, context.getElementsByTagName( tag ) );
} catch ( e ) {
myPush( results, context.getElementsByTagName( tag ) );
}
return results;
};
var getId = function ( id, results ) {
results = results || [];
results.push( document.getElementById( id ) );
return results;
};
var getClass = function ( className, context, results ) {
results = results || [];
if ( document.getElementsByClassName ) {
results.push.apply( results, context.getElementsByClassName( className ) );
} else {
each( getTag( '*', context ), function ( i, v ) {
if ( ( ' ' + v.className + ' ' )
.indexOf( ' ' + className + ' ' ) != -1 ) {
results.push( v );
}
} );
}
return results;
};
// 对each方法的封装
var each = function ( arr, fn ) {
for ( var i = 0; i < arr.length; i++ ) {
if ( fn.call( arr[ i ], i, arr[ i ] ) === false ) {
break;
}
}
};
//对myTrim方法的封装，去空格
var myTrim = function ( str ) {
if ( String.prototype.trim ) {
return str.trim();
} else {
return str.replace( /^\s+|\s+$/g, '' );
}
};
// 通用的get方法
var get = function ( selector, context, results ) {
results = results || [];
context = context || document;
// 1 2 3 4
var rquickExpr = /^(?:#([\w-]+)|\.([\w-]+)|([\w]+)|(\*))$/,
m = rquickExpr.exec( selector );
if ( m ) {
if ( context.nodeType ) {
context = [ context ];
}
// 如果 context 是一个 dom 数组就没有问题了
// 但是 context 是一个选择器字符串. 有可能是 '.c'
//
if ( typeof context == 'string' ) {
context = get( context );
}
each( context, function ( i, v ) {
if ( m[ 1 ] ) {
results = getId( m[ 1 ], results );
} else if ( m[ 2 ] ) {
results = getClass( m[ 2 ], v, results );
} else if ( m[ 3 ] ) {
results = getTag( m[ 3 ], this, results );
} else if ( m[ 4 ] ) {
results = getTag( m[ 4 ], this, results );
}
} );
}
return results;
};
var select = function ( selector, context, results ) {
results = results || [];
// 首先处理逗号
var newSelectors = selector.split( ',' );
// 细节: 一般不考虑两端的空格
each( newSelectors, function ( i, v ) {
results.push.apply( results, get( myTrim( v ), context ) );
} );
//此处我们可以用for in方法进行分解
/*for(var k in newSelectors){
var v = newSelectors[k];
v = myTrim(v)//v.trim();
var list = get(v,context);
results.push.apply(results,list);
}*/
return results;
};
验证以上封装的方法，html如下
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.rect {
width: 400px;
height: 50px;
margin: 10px 0;
}
.c1 {
border: 1px dashed red;
}
.c2 { border: 1px dashed green; }
.c3 { border: 1px dashed blue; }
</style>
<script src="common.js"></script> </head>
<body>
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c3 rect"></div>
<div class="c2 rect"></div>
</div>
<hr />
<div>
<div class="c1 rect"></div>
<div class="c3 rect"></div>
</div>
<hr />
<div class="c">
<div class="c1 rect"></div>
</div>
</body>
<script>
var list = select( '.c1, .c2' );
each( list, function () {
this.style.backgroundColor = 'skyblue';
}); </script>
</html>
5、问题描述：在这我们传入的是后代选择器字符串
思路：假设list = get（'.c .c1',context）,即在context下找出.c，然后再在.c下找出.c1
等价于：list = get（'.c ',context）； list = get（'.c1',list）
var myPush = function( target, els ) {
var j = target.length,
i = 0;
// Can't trust NodeList.length
while ( (target[j++] = els[i++]) ) {}
target.length = j - 1;
};
// 注释: 对基本方法的封装
var getTag = function ( tag, context, results ) {
results = results || [];
try {
results.push.apply( results, context.getElementsByTagName( tag ) );
} catch ( e ) {
myPush( results, context.getElementsByTagName( tag ) );
}
return results;
};
var getId = function ( id, results ) {
results = results || [];
results.push( document.getElementById( id ) );
return results;
};
var getClass = function ( className, context, results ) {
results = results || [];
if ( document.getElementsByClassName ) {
results.push.apply( results, context.getElementsByClassName( className ) );
} else {
each( getTag( '*', context ), function ( i, v ) {
if ( ( ' ' + v.className + ' ' )
.indexOf( ' ' + className + ' ' ) != -1 ) {
results.push( v );
}
} );
}
return results;
};
// 对each方法的封装
var each = function ( arr, fn ) {
for ( var i = 0; i < arr.length; i++ ) {
if ( fn.call( arr[ i ], i, arr[ i ] ) === false ) {
break;
}
}
};
//对myTrim方法的封装，去空格
var myTrim = function ( str ) {
if ( String.prototype.trim ) {
return str.trim();
} else {
return str.replace( /^\s+|\s+$/g, '' );
}
};
// 通用的get方法
var get = function ( selector, context, results ) {
results = results || [];
context = context || document;
// 1 2 3 4
var rquickExpr = /^(?:#([\w-]+)|\.([\w-]+)|([\w]+)|(\*))$/,
m = rquickExpr.exec( selector );
if ( m ) {
if ( context.nodeType ) {
context = [ context ];
}
// 如果 context 是一个 dom 数组就没有问题了
// 但是 context 是一个选择器字符串. 有可能是 '.c'
//
if ( typeof context == 'string' ) {
context = get( context );
}
each( context, function ( i, v ) {
if ( m[ 1 ] ) {
results = getId( m[ 1 ], results );
} else if ( m[ 2 ] ) {
results = getClass( m[ 2 ], v, results );
} else if ( m[ 3 ] ) {
results = getTag( m[ 3 ], this, results );
} else if ( m[ 4 ] ) {
results = getTag( m[ 4 ], this, results );
}
} );
}
return results;
};
var select = function ( selector, context, results ) {
results = results || [];
// 首先处理逗号
var newSelectors = selector.split( ',' );
// 细节: 一般不考虑两端的空格
each( newSelectors, function ( i, v ) {
var list = v.split(' ');
var cont = context;
for(var i = 0;i <list.length;i++){
//如果list[i]是空字符串，会生成一个新数组,则需要进行如下判断
if(list[i] === '') continue;
cont = get(list[i],cont);
}
results.push.apply( results, cont );
} );
return results;
};
验证以上封装的方法，html如下
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.rect {
width: 400px;
height: 50px;
margin: 10px 0;
}
.c1 {
border: 1px dashed red;
}
.c2 { border: 1px dashed green; }
.c3 { border: 1px dashed blue; }
</style>
<script src="common.js"></script> </head>
<body>
<div class="c">
<div class="c1 rect"></div>
<div class="c2 rect"></div>
<div class="c3 rect"><p>123</p></div>
<div class="c2 rect"></div>
</div>
<hr />
<div>
<div class="c1 rect"></div>
<div class="c3 rect"></div>
</div>
<hr />
<div class="c">
<div class="c1 rect"></div>
</div>
</body>
<script>
var list = select( '.c .c2' );
each( list, function () {
this.style.backgroundColor = 'skyblue';
}); </script>
</html>