Question

If the "id":"236" exists in spConfig['attributs'][125]['options'] get the array that is contained in.

How would you do this in jQuery ?

var spConfig = {
    "attributes": {
        "125": {
            "id": "125",
            "code": "pos_colours",
            "label": "Colour",
            "options": [{
                "id": "236",
                "label": "Dazzling Blue",
                "price": "0",
                "oldPrice": "0",
                "products": ["11148"]
            }, {
                "id": "305",
                "label": "Vintage Brown",
                "price": "0",
                "oldPrice": "0",
                "products": ["11786", "11787", "11788", "11789", "11790", "11791", "11792", "11793"]
            }]
        }

    }

Answer 1

Your data structure is slightly complicated, but assuming options.ids are unique, you can use

function foo(arg) {
    var filtered;
    $.each(spConfig.attributes, function() {
        filtered = $(this.options).filter(function() {
            return this.id == arg;
        });
    });
    return (filtered.length) ? filtered[0].products : [];
}

Fiddle

The function to return an empty array when a nonexistent key is passed.

Also, if you have more than one attribute property (other than 125) and want to iterate over them:

function foo(arg) {
    var filtered=[];
    $.each(spConfig.attributes, function() {
        filtered.push($(this.options).filter(function() {
            return this.id == arg;
        }));
    });
    filtered = $(filtered).filter(function() {
        return this.length;
    });
    return (filtered.length) ? filtered[0][0].products : [];
}

Fiddle

Or, if you’ll always access the property attribute[125], you may as well leave it hard-coded for simplicity:

function foo(arg) {
    var filtered = $(spConfig.attributes[125].options).filter(function() {
        return this.id == arg;
    });
    return (filtered.length) ? filtered[0].products : [];
}

Fiddle

Or passing the attribute property name if you need more customization.

function foo(arg, attr) {
    var filtered = $(spConfig.attributes[attr].options).filter(function() {
        return this.id == arg;
    });
    return (filtered.length) ? filtered[0].products : [];
}

Fiddle