在访问属性之前检查对象是否为空[duplicate]

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Test for existence of nested JavaScript object key 48 answers

测试是否存在嵌套的JavaScript对象键48个答案

var how = $('how');
var id = $('myId');
if ((how != null && !how.value.blank()) || myId != null) {
    return true;
} else {
    alert('Error');
}

Is there an easier way to check for not null and checking if the value of that element is blank without having to do both != null and then calling value?

是否有更简单的方法来检查not null并检查该元素的值是否为空而不必同时执行这两个操作!= null然后调用value?

1 个解决方案

#1

Since null is falsy, a slightly shorter version would be

由于null是假的,因此稍微短一些

if((how && !how.value.blank()) || myId != null) { 
  ...
}

Note that the above code and your own snippet both assume that if how exists, it will have a property called value, and will throw an exception if this is not the case.

请注意,上面的代码和您自己的代码段都假定如果存在,它将具有一个名为value的属性,并且如果不是这种情况将抛出异常。

#1