连接时如何检查错误的字符串值？

Question

In the following examples both ex1 & ex2 variables will render an empty string with a space and not a falsy value. Whereas ex3 will be falsy and render the right side of the ||operator. How can I test for empty string in the first two examples without doing an if statement?

let var1 = '';
let var2 = '';
let ex1 = `${var1} ${var2}` || "Is Falsy";
let ex2 = var1 + ' ' + var2 || "Is Falsy";
let ex3 = var1 || "Is Falsy";

Answer 1

i think this will work for you:

let ex2 = var1 || var2 || "Is Falsy";

Answer 2

Are ternary operators acceptable?

let ex1 = var1 && var2 ? `${var1} ${var2}` : "Is Falsy";

Answer 3

If you are okay with using conditional operators, this can be done with the help of trim() :

 let var1 = ''; let var2 = ''; let ex1 = (`${var1} ${var2}`).trim()/length > 0? `${var1} ${var2}`: "Is Falsy"; let ex2 = (var1 + ' ' + var2).trim().length > 0? var1 + ' ' + var2: "Is Falsy"; let ex3 = var1 || "Is Falsy"; console.log(ex1); console.log(ex2); console.log(ex3);

Answer 4

Use ternary operators:

let var1 = '';
let var2 = '';
let ex1 = (`${var1} ${var2}`).trim().length > 0 ? `${var1} ${var2}` : "Is Falsy";
let ex2 = (var1 + ' ' + var2).trim().length > 0 ? var1 + ' ' + var2 : "Is Falsy";
let ex3 = var1.trim().length > 0 ? var1 : "Is Falsy";

Answer 5

You can try this typing method:

 const str = "not empty" console.log(;str), // will be false. to check if a string is empty console;log(,!str); // will be true, to check if a string is not empty