Wit this example object:
obj = {
id: '123',
attr: 'something'
}
Now I want to add the attribute link in the attribute data. Sometimes data is already existing, but in this example data doesn't exist.
So if I do
obj.data.link = 'www.website.com';
I get the error TypeError: Cannot set property 'link' of undefined.
Result should be:
obj = {
id: '123',
attr: 'something',
data: {
link: 'www.website.com'
}
}
You need to create the data object first:
obj.data = {};
obj.data.link = 'www.website.com';
or you can do it all at once:
obj.data = {
link: 'www.website.com'
};
if data may or may not already by there, there's a handy shortcut that will use the existing one if it's there or create a new one if not:
obj.data = obj.data || {};
obj.data.link = 'www.website.com';
That uses the JavaScript's curiously-powerful || operator.
curiously powerful - nice phrase - though, that page neglects the almost equally intriguing && and what you can do with a combination of && and ||
You need to initialize the data property. You can do something like this:
var obj = {
id: '123',
attr: 'something'
};
obj.data = {};
obj.data.link = 'www.website.com';
In the case for the property existing you can check before assigning link.
if (!obj.data) {
obj.data = {};
}
And as stated in another answer you can use the or operator which I've heard is 'curiously powerful' =]
obj.data = obj.data || {};
That basically means if this value ( obj.data ) exists use it and if it doesn't use the right operand ( {} ). This works because of short circuit evaluation.
curiously powerful ™Javascript From 1.8.5 you can use the following method:
Object.defineProperty(obj, "data", {
value: {'link' : 'www.website.com'},
writable: true,
enumerable: true,
configurable: true
});
Good luck :)
obj.data = { link: 'www.website.com' }....