Interchange and processing skills between JSON objects and String in JS

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Interchange and processing skills between JSON objects and String in JS_javascript skills

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May 16, 2016 pm 03:06 PM

JSON：JavaScript 对象表示法（JavaScript Object Notation），其实JSON就是一个JavaScript的对象(Object)而已。

如有不清楚JSON，可以去w3cschool了解http://www.w3school.com.cn/json/

1.在javascript中新建一个字符串(JSON文本)。

var txt = '{ "employees" : [' +
'{ "firstName":"Bill" , "lastName":"Gates" },' +
'{ "firstName":"George" , "lastName":"Bush" },' +
'{ "firstName":"Thomas" , "lastName":"Carter" } ]}';

由于 JSON 语法是 JavaScript 语法的子集，JavaScript 函数 eval() 可用于将 JSON 文本转换为 JavaScript 对象。

eval() 函数使用的是 JavaScript 编译器，可解析 JSON 文本，然后生成 JavaScript 对象。必须把文本包围在括号中，这样才能避免语法错误：

var obj = eval ("(" + txt + ")");

注意：eval() 函数可编译并执行任何 JavaScript 代码。这隐藏了一个潜在的安全问题。

使用 JSON 解析器将 JSON 转换为 JavaScript 对象是更安全的做法。JSON 解析器只能识别 JSON 文本，而不会编译脚本。

在浏览器中，这提供了原生的 JSON 支持，而且 JSON 解析器的速度更快。

较新的浏览器和最新的 ECMAScript (JavaScript) 标准中均包含了原生的对 JSON 的支持。

字符串转json对象：JSON.parse(jsonstr);

json对象转json字符串：JSON.stringify(jsonObj);

JQuery方法：

json字符串转json对象：jQuery.parseJSON(jsonStr);

<html>
<body>
<h2>通过 JSON 字符串来创建对象</h3>
<p>
First Name: <span id="fname"></span><br /> 
Last Name: <span id="lname"></span><br /> 
</p> 
<script type="text/javascript">
var txt = '{"employees":[' +
'{"firstName":"Bill","lastName":"Gates" },' +
'{"firstName":"George","lastName":"Bush" },' +
'{"firstName":"Thomas","lastName":"Carter" }]}';
obj = JSON.parse(txt);
document.getElementById("fname").innerHTML=obj.employees[1].firstName 
document.getElementById("lname").innerHTML=obj.employees[1].lastName 
</script>
</body>
</html>

2.那么如何遍历json数组呢？可以把它当成一个普通的javascript对象来处理。

<html>
<body>
<h2>如何遍历JSON数组</h3>
<div id="result"></div>
<script type="text/javascript">
var txt = '[{"firstName":"Bill","lastName":"Gates" },' +
'{"firstName":"George","lastName":"Bush" },' +
'{"firstName":"Thomas","lastName":"Carter" }]';
var arrayJson = JSON.parse(txt);
var html='';
for(var p in arrayJson){
html+=' firstName:'+arrayJson[p].firstName;
html+=' lastName'+arrayJson[p].lastName;
html+='<br />';
}
document.getElementById("result").innerHTML= html;
</script>
</body>
</html>

ie8(兼容模式),ie7和ie6没有JSON对象，不过http://www.json.org/js.html提供了一个json.js,这样ie8(兼容模式),ie7和ie6就可以支持JSON对象以及其stringify()和parse()方法；你可以在 https://github.com/douglascrockford/JSON-js上获取到这个js，一般现在用json2.js。

ie8(兼容模式),ie7和ie6可以使用eval()将字符串转为JSON对象，

var c='{"name":"Mike","sex":"女","age":"29"}';
var cToObj=eval("("+c+")");
alert(typeof(cToObj));

以上内容是针对JS中JSON对象和String之间的互转及处理技巧，希望对大家有所帮助。接下来给大家补充点知识JavaScript中String和JSON之间的转换。

下面给大家介绍w3c标准的浏览器(如火狐、chrome等)是有一个对象JSON（注意是大写）专门用来处理json的。这个对象有两个函数：

JSON.parse(text) //用于解析json;

JSON.stringify(object) //用于生成json格式;

早期的IE版本没有这个对象，可以去json的官方网站自行下载json2.js对付早期IE版本http://www.JSON.org

下面是之前的一些方法，现在可以弃用了

1.旧方法

function strToJson(str){ 
var json = eval('(' + str + ')'); 
return json; 
}

2.常用

function strToJson(str){ 
return (new Function("return " + str))(); 
}

3.IE不支持的方法

function strToJson(str){ 
return JSON.parse(str); 
}

4.jQuery方法

parseJSON: function( data ) { 
if ( typeof data !== "string" || !data ) { 
return null; 
} 
data = jQuery.trim( data ); 
if ( /^[\],:{}\s]*$/.test(data.replace(/\\(&#63;:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, "@") 
.replace(/"[^"\\\n\r]*"|true|false|null|-&#63;\d+(&#63;:\.\d*)&#63;(&#63;:[eE][+\-]&#63;\d+)&#63;/g, "]") 
.replace(/(&#63;:^|:|,)(&#63;:\s*\[)+/g, "")) ) { 
return window.JSON && window.JSON.parse &#63; 
window.JSON.parse( data ) : 
(new Function("return " + data))(); 
} else { 
jQuery.error( "Invalid JSON: " + data ); 
} 
},

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