JavaScript data type verification method_javascript skills-JS Tutorial-php.cn

JavaScript data type verification method_javascript skills

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Release： 2016-05-16 15:22:36

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Recently, I have a new understanding of the verification of JavaScript data types. It turns out that it can be so simple and so comprehensive.
We have customized isString, isNumber, isDate, isError, isRegExp, isBoolean, isNull, isUndefined, isObject and other methods. Now show the javascript data type verification function and test set you defined:

<!DOCTYPE html> 
<html> 
  <head> 
    <meta charset="utf-8"> 
    <title></title> 
  </head> 
  <body> 
     
  </body> 
<script type="text/javascript"> 
//isString 
//isNumber 
//isDate 
//isError 
//isRegExp 
//直接利用和数据类型来判断 
[].forEach.call(['String','Number','Date','Error','RegExp'],function(name){ 
  this['is'+name]=function(obj){ 
    return toString.call(obj)==='[object '+name+']'; 
  }; 
}); 
//isBoolean 
//true和false需要考虑在内 
Object.prototype.isBoolean=function(obj){ 
  return obj===true||obj===false||toString.call(obj)==='[object Boolean]'; 
}; 
//isNull 
//未找到所指向对象 
Object.prototype.isNull=function(obj){ 
  return obj===null; 
}; 
//isUndefined 
//定义了但是未赋值 
Object.prototype.isUndefined=function(obj){ 
  return obj===void 0; 
}; 
//isObject 
//函数和数组都是对象 
Object.prototype.isObject=function(obj){ 
  var type = typeof obj; 
  return type === 'function' || type === 'object' && !!obj; 
}; 
 
//test 
//isString 
var str="iamstring"; 
var a=isString(str); 
console.log(a);//true 
 
//isNumber 
var b=isNumber(a); 
console.log(b);//false 
 
//isNumber 
var num=4; 
var c=isNumber(num); 
console.log(c);//true 
 
//isRegExp 
var reg=/^[1-9]/; 
var d=isRegExp(reg); 
console.log(d);//true 
 
//isDate 
var date=new Date(); 
var e=isDate(date); 
console.log(e);//true 
 
//isBoolean 
var bool=false; 
var f=isBoolean(bool); 
console.log(f);//true 
 
//isNull 
var nul=document.getElementById("div02"); 
var g=isNull(nul); 
console.log(g);//true 
 
//isUndefined 
var undef; 
var h=isUndefined(undef); 
console.log(h);//true 
 
//isObject 
var obj={"1":"1","2":"2"}; 
var i=isObject(obj); 
console.log(i);//true 
 
</script> 
</html>

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The following is a detailed introduction to judging the data type of JavaScript, which is divided into six data types. Friends in need can come and refer to it. I hope it will be helpful to everyone
1. Determine whether it is an array type
The code is as follows:

<STRONG><script type="text/javascript"> 
//<![CDATA[ 
var a=[0]; 
document.write(isArray(a),'<br/>'); 
function isArray(obj){ 
return (typeof obj=='object')&&obj.constructor==Array; 
} 
//]]> 
</script></STRONG>

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2 Determine whether it is a string type
The code is as follows:

<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>

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3 Determine whether it is a numeric type
The code is as follows:

<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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4 Determine whether it is date type
The code is as follows:

<script type="text/javascript"> 
//<![CDATA[ 
document.write(isDate(new Date()),'<br/>'); 
document.write(isDate(10),'<br/>'); 
function isDate(obj){ 
return (typeof obj=='object')&&obj.constructor==Date; 
} 
//]]> 
</script>

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5 Determine whether it is a function
The code is as follows:

<script type="text/javascript"> 
//<![CDATA[ 
document.write(isFunction(function test(){}),'<br/>'); 
document.write(isFunction(10),'<br/>'); 
function isFunction(obj){ 
return (typeof obj=='function')&&obj.constructor==Function; 
} 
//]]> 
</script>

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6 Determine whether it is an object
The code is as follows:

<script type="text/javascript">
linenum
//<![CDATA[ 
document.write(isObject(new Object()),'<br/>'); 
document.write(isObject(10),'<br/>'); 
function isObject(obj){ 
return (typeof obj=='object')&&obj.constructor==Object; 
} 
//]]> 
</script>

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I hope this article will be helpful to everyone learning JavaScript programming.