I want to check if an "key" is present in a JS object. Is there a way of doing this? +the data can be an arbitrary subbranch within sometree
Example:
var sometree = {
foo : {
data : 1
},
foo2 : {
data : 5
}
}
function checkForKey(key, obj) {
//If I do "checkForKey(5, sometree)", I want the function
//to return "sometree.foo2.data".
}
You'll need something recursive if the object can be an arbitrary depth:
var sometree = {
foo: {
data: 1
},
foo2: {
data: 5
}
}
function checkForValue( value, json, name ) {
var result = checkObject( value, json );
return result ? name +'.'+ result : null;
}
function checkObject( value, json ) {
var keys = Object.keys(json);
for ( var i = 0; i < keys.length; i++ ) {
var key = keys[i];
if ( typeof json[key] === 'object' && json[key] !== null ) {
var result = checkObject( value, json[key] );
if ( result )
return key +'.'+ result;
}
else if ( json[key] === value ) {
return key;
}
}
return null;
}
document.write( checkForValue( 5, sometree, 'sometree' ) );
'.' within the key.
. in key names. It does return the expected string, and if dots need escaping that can be handled in another question.sometree / input variable identifier. I mean, we can argue about it, but there's shortcomings in it, and given that this is beginner question, I would imagine it's dangerous to give him code that definitely doesn't do what he wants in one aspect and probably doesn't in another...Following should work:
function checkForKey(key, json) {
var found = false;
for(var x in json) {
if (json.hasOwnProperty(x)) {
if(json[x][data] == key) {
found = key;
}
}
}
return found;
}
data herein - It's broken code and doesn't go down 2 levels into the object, I am sorry if the downvote offends you.[data] checks the variable data, your code would function as ['data'] instead.The getDeepKeyForValue function can be implemented either in "just give me one" form or "give me all of them". You could also ask this to support complex objects, but I wrote the ones to support simple values. NOTE: because keys can have '.' in them, I return an Array of the key path and let you handle those corner cases. You also can't recover the sometree identified/variable name from within the function. This will work...:
function getDeepKeyForValue (value, object, path) {
var keySet = Object.keys(object || {});
var key;
var result;
path = path || [];
keySetLength = keySet.length;
while (keySetLength--) {
key = keySet[keySetLength];
if (value === object[key]) {
return path.concat(key);
}
result = getDeepKeyForValue(value, object[key], path.concat(key));
if (result) {
return result;
}
}
return null;
}
sometree.foo2.data is a deep path / greater than one hop into the object...sometree looking for a 2-deep value...
valueyou are checking for to also work with sub-objects, or just simple values?