如何在Javascript中通过变量自定义字符串？

Question

I want to print an errormessage using javascript in certain cases. The string is german and the start depends on a variable called blfType which can be "field", "line" or "block" and the string then would be "This field already has this prerequisite" if blfType is field. I tried to do that similiar as I would do it in python:

alert("Das Feld"*(blfType == 'field') + "Die Zeile"*(blfType == 'line') + "Der Block"*(blfType == 'block')+" besitzt diese Vorraussetzung bereits");

But this would just print "NaN besitzt diese Vorraussetzung bereits" . Is there any other way how I can do this in just one line or do I have to do create another Variable that takes the start of the sentence.

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In this case I would do this in python like that:

const gerblfType = "Feld" if blfType === "field" else "Zeile" if blfType === "line" else "Block"

But this is also not working. Is there a smooth way in Javascript to not do it like that:

gerblfType = "Feld";
if(blfType == "line") gerblfType = "Zeile";
if(blfType == "block") gerblfType = "Block";

Answer 1

我实际上找到了解决您的第一个问题的方法：

alert("Das Feld".repeat(blfType == 'field') + "Die Zeile".repeat(blfType == 'line') + "Der Block".repeat(blfType == 'block')+" besitzt diese Vorraussetzung bereits");

Answer 2

Use switch instead of if s.

let gerblfType;
switch (blfType) {
  case 'line': gerblfType = 'Die Zeile'; break;
  case 'block': gerblfType = 'Der Block'; break;
  default: gerblfType = 'Das Feld'; break;
}

alert(`${gerblfType} besitzt diese Vorraussetzung bereits`);

Answer 3

Typical ways people would do it.

The if way

 const foo = "two"; let bar = "default"; if(foo === "one") bar = "1"; else if(foo === "two") bar = "2"; console.log(bar);

With nested Ternary

 const foo = "two"; const bar = foo === "one" ? "1" : foo === "two" ? "2" : "default"; console.log(bar);

With an object

 const LOOK_UP = { one: "1", two: "2", default: "default" }; const foo = "two"; const bar = LOOK_UP[foo] || LOOK_UP.default; console.log(bar);