Is it possible to loop through the properties in a JavaScript object? For instance, I have a JavaScript object defined as this:
myObject.options = {
property1: 'value 1',
property2: 'value 2'
};
Properties will get dynamically added to this object. Is there a way for me to just loop through and do a check if a property exists? If so, how?
This question is related to
javascript
lodash
It would be helpful to understand why you need to do this with lodash. If you just want to check if a key exists in an object, you don't need lodash.
myObject.options.hasOwnProperty('property');
If your looking to see if a value exists, you can use _.invert
_.invert(myObject.options)[value]
In ES6, it is also possible to iterate over the values of an object using the for..of
loop. This doesn't work right out of the box for JavaScript objects, however, as you must define an @@iterator property on the object. This works as follows:
for..of
loop asks the "object to be iterated over" (let's call it obj1 for an iterator object. The loop iterates over obj1 by successively calling the next() method on the provided iterator object and using the returned value as the value for each iteration of the loop.Here is an example:
const obj1 = {
a: 5,
b: "hello",
[Symbol.iterator]: function() {
const thisObj = this;
let index = 0;
return {
next() {
let keys = Object.keys(thisObj);
return {
value: thisObj[keys[index++]],
done: (index > keys.length)
};
}
};
}
};
Now we can use the for..of
loop:
for (val of obj1) {
console.log(val);
} // 5 hello
You can definitely do this with vanilla JS like stecb has shown, but I think each
is the best answer to the core question concerning how to do it with lodash.
_.each( myObject.options, ( val, key ) => {
console.log( key, val );
} );
Like JohnnyHK mentioned, there is also the has
method which would be helpful for the use case, but from what is originally stated set
may be more useful. Let's say you wanted to add something to this object dynamically as you've mentioned:
let dynamicKey = 'someCrazyProperty';
let dynamicValue = 'someCrazyValue';
_.set( myObject.options, dynamicKey, dynamicValue );
That's how I'd do it, based on the original description.
Use _.forOwn()
.
_.forOwn(obj, function(value, key) { } );
https://lodash.com/docs#forOwn
Note that forOwn
checks hasOwnProperty
, as you usually need to do when looping over an object's properties. forIn
does not do this check.
For your stated desire to "check if a property exists" you can directly use Lo-Dash's has
.
var exists = _.has(myObject, propertyNameToCheck);
Lets take below object as example
let obj = { property1: 'value 1', property2: 'value 2'};
First fetch all the key in the obj
let keys = Object.keys(obj) //it will return array of keys
and then loop through it
keys.forEach(key => //your way)
just putting all together
Object.keys(obj).forEach(key=>{/*code here*/})
Source: Stackoverflow.com