Shorthand for: assign if not false javascript

Question

looking to see if a shorthand for something I do quite commonly exists.

I commonly write/use functions that will return false if unable to do what they're able to do, but an object if they can. I also might commonly want to check if was successful.

Eg.

function someFunc() {
    // assume a is some object containing objects with or without key b
    // edit: and that a[b] is not going to *want* to be false
    function getAB(a, b) {
        if(a[b]) return a[b];
        return false;
    }

    let ab = getAB(a, b);
    if(!ab) return false;
}

I just wanted to know if there was some kind of shorthand for this. Eg, in fantasy land,

//...
let ab = getAB(a, b) || return false
//...

Not exact but possible dupe: https://stackoverflow.com/questions/15009194/assign-only-if-condition-is-true-in-ternary-operator-in-javascript — Rajesh, Nov 06 '18 at 06:15
In the case of `a = { b: false }`, how is the return result interpreted? — stealththeninja, Nov 06 '18 at 06:26
unsuprisingly, false is falsey so it returns false. kinda just letting that happen though, i can assume that a does not contain false values, i guess. i'll edit for clarity. — Sam Clarke, Nov 06 '18 at 06:29

Bhojendra Rauniyar · Accepted Answer · 2018-11-06T06:24:09.180

1

You can use or operator like:

return a[b] || false

Your full example code can be written as:

function someFunc() {
    // assume a is some object containing objects with or without key b
    function getAB(a, b) {
      return a[b] || false
    }

    return getAB(a, b); // getAB already returns the value, no need to check again.
}

edited Nov 06 '18 at 06:24

answered Nov 06 '18 at 06:11

Bhojendra Rauniyar

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ah, I overlooked. – Bhojendra Rauniyar Nov 06 '18 at 06:12
Why not `return a[b]` then? seems like the OP wants to exit early actually. – Jonas Wilms Nov 06 '18 at 06:24

Shorthand for: assign if not false javascript

1 Answers1