Javascript:使用一个变量,或者如果它是未定义的,则使用默认字符串 [英] Javascript: use either a variable, or if it's undefined, a default string
问题描述
var phrase = function(variable,defaultPhrase){
if(typeof variable ===undefined){
return defaultPhrase;
}
else {
返回变量;
$ / code>
这就是这样调用的:
Ext.Msg.show({title:phrase(js_shutdown,'Shutdown'),// ...
我想要做的是在变量未定义时使用默认短语,但是当我将未定义的变量传递给<$ c $如何解决这个问题?任何其他想法做到这一点?
您不需要函数,通常使用 ||
运算符:
Ext.Msg.show({title:js_shutdown ||'Shutdown',// ...
您可以看到 ||
为:
someValue || defaultValue
对于字符串, defaultValue 如果
someValue ===
。
,则使用code>所有,你需要内嵌 typeof x ===undefined
检查,因为你不能将该变量传递给一个函数(这是一个 ReferenceError
)。
I have this code:
var phrase = function (variable, defaultPhrase) {
if (typeof variable === "undefined") {
return defaultPhrase;
}
else {
return variable;
}
}
It's called like this:
Ext.Msg.show({title: phrase(js_shutdown,'Shutdown'), //...
What I want to do is to use a default phrase when the variable is not defined, but when I pass an undefined variable to phrase()
, JS throws an undefined variable error. How do I fix this? Any other ideas to do this?
You don't need a function. The ||
operator is usually used:
Ext.Msg.show({ title: js_shutdown || 'Shutdown', //...
You can see ||
as:
someValue || defaultValue
For strings, defaultValue
is used if someValue === ""
.
If the variable is not defined at all, you'll need to inline the typeof x === "undefined"
check, because you cannot pass the variable to a function (that's a ReferenceError
).
这篇关于Javascript:使用一个变量,或者如果它是未定义的,则使用默认字符串的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!