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select.js
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// xxxxx
// 选择器引擎
var select =
(function() {
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;
};
// 对循环的封装
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]+)|(\*))$/,
m = rquickExpr.exec(selector);
if (m) {
if (context.nodeType) {
context = [context];
}
// 如果 context 是一个 dom 数组就没有问题了
// 但是 context 是一个选择器字符串. 有可能是 '.c'
//
if (typeof context == 'string') {
context = get(context);
}
each(context, function(i, v) {
if (m[1]) {
results = getId(m[1], results);
} else if (m[2]) {
results = getClass(m[2], v, results);
} else if (m[3]) {
results = getTag(m[3], this, results);
} else if (m[4]) {
results = getTag(m[4], this, results);
}
});
}
return results;
};
var myTrim = function(str) {
if (String.prototype.trim) {
return str.trim();
} else {
return str.replace(/^\s+|\s+$/g, '');
}
};
var select = function(selector, context, results) {
results = results || [];
// 首先处理逗号
var newSelectors = selector.split(','); // => [ '.dv .c1', ' .c2' ]
each(newSelectors, function(i, v) {
// 需要解析的就是 v 或 this
// 分割
var list = v.split(' ');
var c = context;
// context -> list[ 0 ] -> list[ 1 ] -> ... -> list[ length - 1 ]
for (var i = 0; i < list.length; i++) {
if (list[i] === '') continue;
c = get(list[i], c);
// 如果 list[ i ] 是空字符串, 那么只是下 c 下面找空数据, 是不会报错的
}
results.push.apply(results, c);
});
return results;
};
return select;
})();