将空字符串分配给 javascript 变量
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Assign empty string to javascript variable
提问by Vetri Manoharan
I get return value as null and assign that value it shows as null in the UI. But I want to check some condition and if it is null, it should not show up anything.. I tried the below code and it doesn't work
我将返回值设为 null 并分配该值，它在 UI 中显示为 null。但我想检查一些条件，如果它为空，它不应该显示任何东西..我尝试了下面的代码，但它不起作用
var companyString;
if(utils.htmlEncode(item.companyname) == null)
{
companyString = '';
}
else{
companyString = utils.htmlEncode(item.companyname);
}采纳答案by user2864740
Compare item.companynameto null (but probably really any false-y value) - and notthe encoded form.
比较item.companyname为null（但可能确实存在任何虚假记载，Y值） -和未编码形式。
This is because the encoding will turn nullto "null"(or perhaps "", which are strings) and "null" == null(or any_string == null) is false.
这是因为编码会变成null到"null"（或者也许""，这是字符串）和"null" == null（或any_string == null）是假的。
Using the ternary operator it can be written as so:
使用三元运算符可以这样写：
var companyString = item.companyname
? utils.htmlEncode(item.companyname)
: "";
Or with coalescing:
或合并：
var companyString = utils.htmlEncode(item.companyname ?? "");
Or in a long-hand form:
或者以长手形式：
var companyString;
if(item.companyname) // if any truth-y value then encode
{
companyString = utils.htmlEncode(item.companyname);
}
else{ // else, default to an empty string
companyString = '';
}
回答by Panther
var companyString;
if(item.companyname !=undefined && item.companyname != null ){
companyString = utils.htmlEncode(item.companyname);
}
else{
companyString = '';
}
Better to check not undefinedalong with not nullin case of javascript. And you can also put alertor console.logto check what value you are getting to check why your if block not working. Also, utls.htmlEncode will convert your nullto String having null literal, so compare without encoding.
最好not undefined与not nulljavascript一起检查。你也可以输入alert或console.log检查你得到的值来检查为什么你的 if 块不起作用。此外，utls.htmlEncode 会将您null的字符串转换为具有 的字符串null literal，因此无需编码即可进行比较。
回答by AkshayJ
var companyString="";
if(utils.htmlEncode(item.companyname) != null)
{
companyString = utils.htmlEncode(item.companyname);
}
