Regex: split object notation path string with array support

Question

I've got a recursive function to go through an object and take what is needed using path string like jsonObj.object.item.value. The idea is to upgrade it somehow to support arrays.

const getValue = function(pathVar, obj) {
  obj = obj || x;
  // get very first node and the rest
  let [node, restNodes] = pathVar.split(/\.(.+)/, 2)
  // get interim object
  ret = obj[node];
  if(ret === undefined) return undefined;
  // pass rest of the nodes further with interim object
  if(restNodes) return getValue(restNodes, ret);
  return ret;
};

Right now on each iteration simple regexp splits path string like jsonObj.object.item.value into jsonObj and object.item.value

the idea is to add array support here, so I can do transformations like

car.engine.something => car and engine.something
wheels[2].material.name => wheels and [2].material.name
[2].material.name => 2 and material.name
car.wheels[4] => car and wheels[4]

Any ideas how to do it?

why do you want to re-invent the wheel? there is _.get method that does exactly that, lodash.com/docs/4.17.11#get — felixmosh
– felixmosh, Commented May 29, 2019 at 15:11

Ranga · Accepted Answer · 2019-05-29 15:57:07Z

1

You could use eval which will just evaluate the expression. As for a functional approach, use the following.

function getValue(path, obj) {
    obj = obj || self; // self is the global window variable
    if( !path )
        return obj;

    let pattern = /(?:\["?)?(\w+)(?:\.|"?])?(.*)/i;

    let [ full, property, rest ] = path.match(pattern);
    return getValue( rest, obj[ property ] );
}

self.obj = { foo: [ 2, {bar: "baz"} ] };
console.log(getValue('obj.foo[1]["bar"]')) // 'baz'

Pattern uses four groups. The first is non-capturing and expects a possible ["this will help match array or object properties. Then we expect a series of alphanumerics which we capture. Then another non capturing group to either close "] or match a .. Finally we capture the rest to use in the next call.

Again eval is capable of all of this.

answered May 29, 2019 at 15:57

Ranga

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