Javascript TRUE 未定义或在引号中
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Javascript TRUE is not defined or in quotes
提问by John Magnolia
I have a XML file that contains
我有一个 XML 文件，其中包含
<car>
<id>123</id>
<sunroof>FALSE</sunroof>
<service>TRUE</service>
</car>
The following code only works if I wrap TRUE inside quotes e.g (service == "TRUE")
以下代码仅在我将 TRUE 包裹在引号内时才有效，例如 (service == "TRUE")
var service = tis.find("service").text();
if(service === TRUE){
var service_tag = '<a title="Service" href="">Service</a>'
} else {
var service_tag = '';
}
回答by JaredPar
Without quotes javascript will try to interpret TRUEas a value / expression. There is no value TRUEnatively defined in javascript. There is truebut javascript is case sensitive so it won't bind TRUEto true.
如果没有引号，javascript 将尝试解释TRUE为值/表达式。TRUEjavascript 中没有本机定义的值。有true但是 javascript 区分大小写，所以它不会绑定TRUE到true.
The value you get back from text()is a stringprimitive. Writing "TRUE"gives you back the string"TRUE"which does compare succesfully with the value service
你从中得到的值text()是一个string原始值。写作"TRUE"会返回string"TRUE"与价值比较成功的那个service
回答by MeLight
JavaScript boolean trueand falseare lower case.
JavaScript 布尔值true和false小写。
回答by WEFX
Set service equal to this, so JavaScript will be able to interpret your values:
将 service 设置为与此相等，以便 JavaScript 能够解释您的值：
var service = tis.find("service").text().toLowerCase();
回答by Sajith Nair
var service = tis.find("service").text();
This returns a string "TRUE". Since === checks for the type as well, it always returns false.
这将返回一个字符串“TRUE”。因为 === 也会检查类型，所以它总是返回 false。
回答by Andrew Wilkinson
TRUErefers to a variable named TRUEwhich doesn't exist, so you get an error. "TRUE"is a string containing the characters TRUE. Your variable servicewill contain a string, so the second of these are what you want.
TRUE引用一个TRUE不存在的命名变量，所以你会得到一个错误。"TRUE"是一个包含字符的字符串TRUE。您的变量service将包含一个字符串，因此其中的第二个就是您想要的。
回答by Roberto Alarcon
its because the tripe equal also check for type, and TRUE it's a identifier "TRUE" is a value
它是因为牛肚等于也检查类型，并且 TRUE 它是一个标识符“TRUE”是一个值
// this will work
if(service === "TRUE"){
var service_tag = '<a title="Service" href="">Service</a>'
} else {
var service_tag = '';
}
回答by Quentin
This is expected.
这是预期的。
tis.find("service").text();returns a string, not a boolean, and the JavaScript boolean for truth is true(which is case sensitive, like everything else in the language).
tis.find("service").text();返回一个字符串，而不是一个布尔值，并且 JavaScript 布尔值是true（它区分大小写，就像语言中的其他所有内容一样）。
