JS How to Determine If an Object Contains an Attribute

  • 2021-08-09 06:44:38
  • OfStack

1. Using in keyword will return true/false pro-test can be realized!

// Create an object  data 

var data = scope.data;

// Judge update The value is' Yes ' When, data There must be in it 'userXM'  And  'mobile'  Two fields, and neither is empty 
    if(scope.update == " Yes "){
    if(!('userXM' in data)||!( 'mobile' in data)){
     // Code that does not contain fields, executes 
   }else if(data["userXM"] == ""|| data["mobile"] == ""){

        // Two values, or where 1 Code executed when the value is null 
var obj = {name:'jack'};
alert('name' in obj); // --> true
alert('toString' in obj); // --> true

2. hasOwnProperty method

This method returns a Boolean value indicating whether the object has the specified property in its own properties (that is, whether it has the specified key).

var obj = {name:'jack'};
obj.hasOwnProperty('name'); // --> true
obj.hasOwnProperty('toString'); // --> false

3. Use undefined to judge

var o={x:1};
o.x!==undefined; //true
o.y!==undefined; //false
o.toString!==undefined //true

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