"string1" + ()?"string2":"string3"

Question

var str1 = "string1" + (false)?"string2":"string3";   // output: string2
var str2 = "string1" + (true)?"string2":"string3";    // output: string2

Why do these expressions evaluate to "string2" regardless of true/false in the condition?

What happens to "string1" and "string3" ? How exactly are these expressions being evaluated?

Read up on operator precedence first before asking a question. — kapa, Jul 18 '14 at 14:40

score 8 · Accepted Answer · answered Jul 18 '14 at 14:39

8

Because ? has less precedence than +

"string1" + (false)?"string2":"string3"

is equivalent to saying:

("string1" + false) ? "string2" : "string3"

"string1" + false evaluates to the string value "string1false" which is truthy (Thanks @Vache)

To get it to work the way you want, add braces around the ternary expression.

"string1" + (false  ? "string2" : "string3")

answered Jul 18 '14 at 14:39

techfoobar

4

I'd add that `"string1" + false` produces the string `"string1false"` which is a truthy value. – dee-see Jul 18 '14 at 14:40
@Vache - Good addition. Thank you. – techfoobar Jul 18 '14 at 14:42

1 Answers1