Javascript 使用 underscore.js 进行空值检查
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Using underscore.js for null checking
提问by John Cooper
var name = "someName";
if(name !=null) {
// do something
}
- I am right now using http://underscorejs.org/#isNull, how would i do
the same using
underscore.js - Does it give any slight improvement in terms of performance for such functions.
- 我现在正在使用http://underscorejs.org/#isNull，我将如何使用
underscore.js - 它是否在此类功能的性能方面略有改进。
回答by Peter Olson
In underscore, you can use
在下划线中，您可以使用
if(!_.isNull(name)) {}
and in plain Javascript, you should use
并且在纯 Javascript 中，您应该使用
if(name !== null) {}
You should avoid the loose inequality operator !=because it does type coercion and undefined != nullwill return false.
您应该避免使用松散的不等式运算符，!=因为它确实输入了强制类型并且undefined != null会返回false。
Using plain Javascript is slightly faster because it doesn't have to invoke a function, but it will be imperceptible and it should hardly be a consideration.
使用普通 Javascript 稍微快一点，因为它不必调用函数，但它不会被察觉，几乎不应该考虑。
I don't have a strong preference either way as far as readability goes, but it seems a little excessive and verbose to call a library function for such a simple check.
就可读性而言，我对任何一种方式都没有强烈的偏好，但为这样一个简单的检查调用库函数似乎有点过分和冗长。
回答by Chuck Norris
In underscore.js you must write this to achieve that functionality.
在 underscore.js 中，您必须编写它来实现该功能。
var name = "someName";
if(!(_.isNull(name ))) {
// do something
}
In underscore.js function isNullis written like this
在 underscore.js 函数isNull是这样写的
_.isNull = function(obj) {
return obj === null;
};
So the difference is using ==in your code and ===in underscore.js.For more details about that difference you can look in this question.
所以区别在于==在您的代码和===underscore.js 中使用。有关该区别的更多详细信息，您可以查看此问题。
Which equals operator (== vs ===) should be used in JavaScript comparisons?
在 JavaScript 比较中应该使用哪个等于运算符 (== vs ===)？
P.S. I will suggest to write your own condition instead of using any library in such simple place.
PS 我会建议写你自己的条件，而不是在这样简单的地方使用任何库。
var name = "someName";
if(name !== null)) {
// do something
}
回答by Niet the Dark Absol
Well your original code is flawed because if nameis an empty string, false, the number 0or any other falsy value then it will be considered nullas far as your test is concerned.
好吧，您的原始代码有缺陷，因为如果name是空字符串、false数字0或任何其他虚假值，那么就null您的测试而言，它将被考虑在内。
As a general rule, calling ANY function is an overhead that should be avoided if possible. In this case, calling a function just to test if a value is null, when you could very easily just write if( name === null), is just stupid, IMO...
作为一般规则，调用 ANY 函数是一种应该尽可能避免的开销。在这种情况下，调用一个函数只是为了测试一个值是否为空，当你可以很容易地编写时if( name === null)，只是愚蠢的，IMO...
回答by Ashutosh Soni
if ((!(_.isUndefined(data)) || _.isEmpty(data))) {
//Valid Data
}else {//Not Valid}
