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js contains five data types number string boolean undefinedobject and function type function
You will definitely ask when you see this: How do I distinguish between objects, arrays and What about null?
Next we will use a sharp tool: Object.prototype.toString.call
This is a native prototype extension function of the object, used to distinguish more accurately type of data.
Let’s try this thing:
var gettype=Object.prototype.toString
gettype.call(' aaaa') Output [object String]
gettype.call(2222) Output [object Number]
gettype.call(true) Output [object Boolean]
gettype. call(undefined) Output [object Undefined]
gettype.call(null) Output [object Null]
gettype.call({}) Output [object Object]
gettype.call([]) Output [object Array]
gettype.call(function(){}) Output [object Function]
Seeing this, we have solved the problem just now.
In fact, there are many type judgments in js
[object HTMLpElement] p object,
[object HTMLBodyElement] body object,
[object Document] (IE) or
[object HTMLDocument] (firefox, google)...
Judgement of various dom nodes, these things will be used when we write plug-ins.
The methods that can be encapsulated are as follows:
var gettype=Object.prototype.toString var utility={ isObj:function(o){ return gettype.call(o)=="[object Object]"; }, isArray:function(o){ return gettype.call(o)=="[object Array]"; }, isNULL:function(o){ return gettype.call(o)=="[object Null]"; }, isDocument:function(){ return gettype.call(o)=="[object Document]"|| [object HTMLDocument]; } ........ }
1 Determine whether it is an array type
<script type="text/javascript"> //<![CDATA[ var a=[0]; document.write(isArray(a),'<br/>'); function isArray(obj){ return (typeof obj=='object')&&obj.constructor==Array; } //]]> </script>
2 Determine whether It is a string type
<script type="text/javascript"> //<![CDATA[ document.write(isString('test'),'<br/>'); document.write(isString(10),'<br/>'); function isString(str){ return (typeof str=='string')&&str.constructor==String; } //]]> </script>
3 Determine whether it is a numeric type
<script type="text/javascript"> //<![CDATA[ document.write(isNumber('test'),'<br/>'); document.write(isNumber(10),'<br/>'); function isNumber(obj){ return (typeof obj=='number')&&obj.constructor==Number; } //]]> </script>
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