javascript if (a.b.v.c.d.e === true)

Question

What's an easy way to check

if (a.b.v.c.d.e === true) {}

and return false if any of b or c or v is undefined?

Coffeescript handles it easily but what is a comparable solution in vanilla javascript? Is there a library that has this common issue taken cared of?

What about `if ( undefined !== a.b.c.d.e && true === a.b.c.d.e ) { }` If you try to access any value that doesn't exists will return `undifined`. — KodeFor.Me, Mar 01 '16 at 17:43
@Merianos, if either `a`, `b`, `c` or `d` is undefined, the code you posted will throw an exception. — Frédéric Hamidi, Mar 01 '16 at 17:45
@Merianos, if they exist and are bound to `undefined`, or if they don't exist in the "parent" object. — Frédéric Hamidi, Mar 01 '16 at 17:47

score 1 · Answer 1 · answered Mar 01 '16 at 17:42

1

Javascript does not have a pretty feature to do this (without using any helper functions). You can use && operator to do this:

if (a && a.b && a.b.v && a.b.v.c && a.b.v.c.d && a.b.v.c.d.e === true) {}

answered Mar 01 '16 at 17:42

madox2

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score 1 · Answer 2 · answered Mar 01 '16 at 17:42

1

You can use the short-circuiting behavior of && to express the chained dependencies.

if (a && a.b && a.b.v && a.b.v.c && a.b.v.c.d && a.b.v.c.d.e === true)

answered Mar 01 '16 at 17:42

Barmar

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Leventix · Answer 3 · 2016-03-01T17:48:32.537

1

Write a function and call it like this:

if (ignoreNulls(a, 'b', 'v', 'c', 'd', 'e') == true) {
  // ...
}


function ignoreNulls() {
  var args = Array.prototype.slice.call(arguments);
  var subj = args.shift();
  while (prop = args.shift()) {
    var v = subj[prop];
    if (v !== null && v != undefined) {
      subj = v
    } else {
      return null;
    }
  }
  return subj;
}

edited Mar 01 '16 at 17:48

answered Mar 01 '16 at 17:43

Leventix

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javascript if (a.b.v.c.d.e === true)

3 Answers3