How can I access a multi-level property if I am using a variable as the key?
This is not working:
var obj = {
first: {thirst: "yo"},
second: {beckon: "dud"}
}
var key = "first.thirst";
var result = obj[key];
3 Answers
When you use a string as a property name in JavaScript, there are no characters that are off-limits: including the period. So you can easily have an object property like this:
var o = {
'first.second.third': 'value';
}
Given this, it's clearly not possible to implement your solution.
However, as long as you don't use periods in your property naming, you can create a function that does this:
function resolve(obj, path){
path = path.split('.');
var current = obj;
while(path.length) {
if(typeof current !== 'object') return undefined;
current = current[path.shift()];
}
return current;
}
Then you could call:
var key = "first.thirst";
var result = resolve(obj, key);
Comments
You can traverse the tree, as @RobW said:
var traverse = function (obj, keys) {
return keys.split('.').reduce(function (cur, key) {
return cur[key];
}, obj);
};
var obj = {
first: { thirst: 'yo' },
second: { beckon: 'dud' }
};
var keys = 'first.thirst';
console.log(traverse(obj, keys));
2 Comments
EricC
Oh, no easy one-line fix :( But at least this will work! Thanks to you all!
Ethan Brown
Two comments. First,
traverse is a poor name: the fact that this function is traversing the object tree is only an implementation detail. What it's actually doing is resolving a path within the object; it just so happens to be using an abortive depth-first traversal. Secondly, this function will throw an exception if the path isn't valid. Perhaps that's what you want, but in JavaScript, usually not. Otherwise, nice work!function getMultiLevelProp(obj, key){
if(typeof obj == "object"){
var keyQueue = key.split(".").reverse();
var tempVal = obj, currentKey;
while((currentKey = keyQueue.pop()) != undefined)
tempVal = tempVal[currentKey];
return tempVal;
}
return false;}
this could work
evalor write a custom function that traverses the tree.