javascript 检查对象是否在javascript中具有一组属性
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Check if object has a set of properties in javascript
提问by Ben
Let's say I have an object named a, how could I check that ahas a specific list of multiple properties in shorthand, I think it can be done using inlogical operator,
比方说，我有一个名为对象a，我怎么能检查a在速记多个属性的具体名单，我认为这是可以做到用在逻辑运算符，
Something like this:
像这样的东西：
var a = {prop1:{},prop2:{},prop3:{}};
if ({1:"prop1",2:"prop2",3:"prop3"} in a)
console.log("a has these properties:'prop1, prop2 and prop3'");
EDIT
编辑
If plain javascript can't help, jQuery will do, but i prefer javascript
如果普通的 javascript 无济于事，jQuery 可以，但我更喜欢 javascript
EDIT2
编辑2
Portability is the privilege
便携性是特权
回答by p.s.w.g
The simplest away is to use a conventional &&:
最简单的方法是使用传统的&&：
if ("prop1" in a && "prop2" in a && "prop3" in a)
console.log("a has these properties:'prop1, prop2 and prop3'");
This isn't a 'shorthand', but it's not that much longer than what you've proposed.
这不是“速记”，但它并没有比您提出的长多少。
You can also place the property names you want to test in an array and use the everymethod:
您还可以将要测试的属性名称放在数组中并使用以下every方法：
var propertiesToTest = ["prop1", "prop2", "prop3"];
if (propertiesToTest.every(function(x) { return x in a; }))
console.log("a has these properties:'prop1, prop2 and prop3'");
Note however, that this was introduced in ECMAScript 5, so it is not available on some older browsers. If this is a concern, you can provide your own version of it. Here's the implementation from MDN:
但是请注意，这是在 ECMAScript 5 中引入的，因此在某些较旧的浏览器上不可用。如果这是一个问题，您可以提供您自己的版本。这是 MDN 的实现：
if (!Array.prototype.every) {
Array.prototype.every = function(fun /*, thisp */) {
'use strict';
var t, len, i, thisp;
if (this == null) {
throw new TypeError();
}
t = Object(this);
len = t.length >>> 0;
if (typeof fun !== 'function') {
throw new TypeError();
}
thisp = arguments[1];
for (i = 0; i < len; i++) {
if (i in t && !fun.call(thisp, t[i], i, t)) {
return false;
}
}
return true;
};
}
回答by Dexygen
This is where the underscore.js libraryreally shines. For instance it provides an already poly-filled every()method as suggested in a comment to p.s.w.g.'s answer: http://underscorejs.org/#every
这是underscore.js 库真正闪耀的地方。例如，它提供了一个已经填充的every()方法，如对 pswg 答案的评论中所建议的：http://underscorejs.org/#every
But there's more than one way to do it; the following, while more verbose, may also suit your needs, and exposes you to more of what underscore can do (e.g. _.keys and _.intersection)
但是有不止一种方法可以做到；以下虽然更冗长，但也可能适合您的需求，并让您了解下划线可以做的更多事情（例如 _.keys 和 _.intersection）
var a = {prop1:{},prop2:{},prop3:{}};
var requiredProps = ['prop1', 'prop2', 'prop3'];
var inBoth = _.intersection(_.keys(a), requiredProps);
if (inBoth.length === requiredProps.length) {
//code
}
回答by sachinjain024
Use Array.reducelike this:
像这样使用Array.reduce：
var testProps = ['prop1', 'prop2', 'prop3'];
var a = {prop1:{},prop2:{},prop3:{}};
var result = testProps.reduce(function(i,j) { return i && j in a }, true);
console.log(result);
回答by StackSlave
Like this:
像这样：
var testProps = ['prop1', 'prop2', 'prop3', 'prop4'];
var num = -1, outA;
for(var i in a){
if(i === testProps[++num])outA[num] = i;
}
console.log('properties in a: '+outA.join(', '));
回答by Ringo
I think it's good to try it:
我觉得可以试试：
/* Create an object class */
var obj = function(){ this.attributes = new Array(); }
obj.prototype.addProp = function(value){ this.attributes.push(new attribute(value)); }
obj.prototype.hasProp = function(value){
for(var i = 0; i < this.attributes.length; i++){
if(value == this.attributes[i].value) return true; } return false; }
function attribute(value){
this.value = value;
}
/* Testing object has some value*/
var ob = new obj();
ob.addProp('1');
ob.addProp('2');
ob.addProp('3');
//* check value index
//alert(ob.attributes[0].value);
//* check if ob has prop
alert(ob.hasProp('1'));
Here is DEMO
这是演示
回答by Mark Tyers
Slightly more elegant use of the Object.every()prototype function to include try-catch:
稍微优雅地使用Object.every()原型函数来包括try-catch：
try {
const required = ['prop1', 'prop2', 'prop3']
const data = {prop1: 'hello', prop2: 'world', prop3: 'bad'}
if (!required.every( x => x in data )) throw new Error('missing property')
console.log('all properties found')
} catch(err) {
console.log(err.message)
}
``
