分享原生JavaScript技巧大收集(91~100)

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文章来源：jquery教程 - http://www.jq-school.com/Show.aspx?id=315

不知不觉就收集了100个实用的JavaScript代码片段，希望可以帮到支持JquerySchool网站的网友和jquery学堂所有群的成员们。

91、原生JavaScript实现窗体改变事件resize的操作（兼容所以的浏览器）

(function(){
	var fn = function(){
		var w = document.documentElement ? document.documentElement.clientWidth : document.body.clientWidth
			,r = 1255
			,b = Element.extend(document.body)
			,classname = b.className;
		if(w < r){
			//当窗体的宽度小于1255的时候执行相应的操作
		}else{
			//当窗体的宽度大于1255的时候执行相应的操作
		}
	}
	if(window.addEventListener){
		window.addEventListener('resize', function(){ fn(); });
	}else if(window.attachEvent){
		window.attachEvent('onresize', function(){ fn(); });
	}
	fn();
})();

92、原生JavaScript用正则清除空格分左右

function ltrim(s){ return s.replace( /^(\s*|　*)/, ""); } 
function rtrim(s){ return s.replace( /(\s*|　*)$/, ""); } 
function trim(s){ return ltrim(rtrim(s));} 

93、原生JavaScript判断变量是否空值

/**
 * 判断变量是否空值
 * undefined, null, '', false, 0, [], {} 均返回true，否则返回false
 */
function empty(v){
    switch (typeof v){
        case 'undefined' : return true;
        case 'string'    : if(trim(v).length == 0) return true; break;
        case 'boolean'   : if(!v) return true; break;
        case 'number'    : if(0 === v) return true; break;
        case 'object'    : 
            if(null === v) return true;
            if(undefined !== v.length && v.length==0) return true;
            for(var k in v){return false;} return true;
            break;
    }
    return false;
}

94、原生JavaScript实现base64解码

function base64_decode(data){
	var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
	var o1, o2, o3, h1, h2, h3, h4, bits, i = 0,ac = 0,dec = "",tmp_arr = [];
	if (!data) { return data; }
	data += '';
	do { 
		h1 = b64.indexOf(data.charAt(i++));
		h2 = b64.indexOf(data.charAt(i++));
		h3 = b64.indexOf(data.charAt(i++));
		h4 = b64.indexOf(data.charAt(i++));
		bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;
		o1 = bits >> 16 & 0xff;
		o2 = bits >> 8 & 0xff;
		o3 = bits & 0xff;
		if (h3 == 64) {
			tmp_arr[ac++] = String.fromCharCode(o1);
		} else if (h4 == 64) {
			tmp_arr[ac++] = String.fromCharCode(o1, o2);
		} else {
			tmp_arr[ac++] = String.fromCharCode(o1, o2, o3);
		}
	} while (i < data.length);
	dec = tmp_arr.join('');
	dec = utf8_decode(dec);
	return dec;
}

95、原生JavaScript实现utf8解码

function utf8_decode(str_data){
	var tmp_arr = [],i = 0,ac = 0,c1 = 0,c2 = 0,c3 = 0;str_data += '';
	while (i < str_data.length) {
		c1 = str_data.charCodeAt(i);
		if (c1 < 128) {
			tmp_arr[ac++] = String.fromCharCode(c1);
			i++;
		} else if (c1 > 191 && c1 < 224) {       
			c2 = str_data.charCodeAt(i + 1);
			tmp_arr[ac++] = String.fromCharCode(((c1 & 31) << 6) | (c2 & 63));
			i += 2;
		} else {
			c2 = str_data.charCodeAt(i + 1);
			c3 = str_data.charCodeAt(i + 2);
			tmp_arr[ac++] = String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
			i += 3;
		}
	} 
	return tmp_arr.join('');
}

96、原生JavaScript获取窗体可见范围的宽与高

function getViewSize(){
	var de=document.documentElement;
	var db=document.body;
	var viewW=de.clientWidth==0 ?  db.clientWidth : de.clientWidth;
	var viewH=de.clientHeight==0 ?  db.clientHeight : de.clientHeight;
	return Array(viewW ,viewH);
}

97、原生JavaScript判断IE版本号（既简洁、又向后兼容！）

var _IE = (function(){
    var v = 3, div = document.createElement('div'), all = div.getElementsByTagName('i');
    while (
        div.innerHTML = '',
        all[0]
    );
    return v > 4 ? v : false ;
}());

98、原生JavaScript获取浏览器版本号

function browserVersion(types) {
    var other = 1;
    for (i in types) {
        var v = types[i] ? types[i] : i;
        if (USERAGENT.indexOf(v) != -1) {
            var re = new RegExp(v + '(\\/|\\s|:)([\\d\\.]+)', 'ig');
            var matches = re.exec(USERAGENT);
            var ver = matches != null ? matches[2] : 0;
            other = ver !== 0 && v != 'mozilla' ? 0 : other;
        } else {
            var ver = 0;
        }
        eval('BROWSER.' + i + '= ver');
    }
    BROWSER.other = other;
}

99、原生JavaScript半角转换为全角函数

function ToDBC(str){
  var result = '';
  for(var i=0; i < str.length; i++){
    code = str.charCodeAt(i);
    if(code >= 33 && code <= 126){
      result += String.fromCharCode(str.charCodeAt(i) + 65248);
    }else if (code == 32){
      result += String.fromCharCode(str.charCodeAt(i) + 12288 - 32);
    }else{
      result += str.charAt(i);
    }
  }
 return result;
}

100、原生JavaScript全角转换为半角函数 

function ToCDB(str){
  var result = '';
  for(var i=0; i < str.length; i++){
    code = str.charCodeAt(i);
    if(code >= 65281 && code <= 65374){
      result += String.fromCharCode(str.charCodeAt(i) - 65248);
    }else if (code == 12288){
      result += String.fromCharCode(str.charCodeAt(i) - 12288 + 32);
    }else{
      result += str.charAt(i);
    }
  }
 return result;
}