What is the Javascript equivalent of writing 'If not"

Question

Python programmer here.

I don't know how to write this. I tried using 'if !in' and '!if in', but I don't know how. Tried to Google it but got no results.

Based on your previous questions, you already know that parentheses are required. Are you actually trying to write a "if not in (array)" condition? — JJJ, Nov 08 '16 at 18:29

Derek 朕會功夫 · Answer 1 · 2016-11-08T18:39:58.123

2

The correct syntax is

if(!condition){
    expression();
}

Note that you need parenthesis around the condition.

@plalx wants a formal definition, and here you go:

IfStatement:
    if(Expression) Statement else Statement
    if(Expression) Statement

In case of any ambiguity the else would be matched with the nearest if.

edited Nov 08 '16 at 18:39

answered Nov 08 '16 at 18:28

1

Why not expressing your comment in the code rather than making it a comment? `if (!(condition)) { ... }` Commenting rather than making code explicit is a very bad habit most programmers have... ;) – plalx Nov 08 '16 at 18:30
1

@plalx I believe this is the cleanest way to demonstrate the syntax. – Derek 朕會功夫 Nov 08 '16 at 18:31
How could it be the cleanest if you need an additional comment? This sounds like, to perform some process you need to: `doThis() //by the way you also need to doThat() before calling doThis()`. It's much cleaner to just `doThat(); doThis();` – plalx Nov 08 '16 at 18:33

score 0 · Answer 2 · answered Nov 08 '16 at 18:33

If you have some value:

var excludeMe = "something unwanted";

Then you can use the following if statement:

if(myTestCase !== excludeMe) { //do something...}

Keep in mind that != does not check type and !== does check type. So, 1 != "1" is false and 1 !== "1" is true.

2 Answers2