I have some data that I want to iterate through and reject those with a disabled: true property.

however when I try _.reject my object gets turned into an array.

var data = {
  stuff: {
     item1: {
        name: "one",
        disabled: true
     },
     item2: {
        name: "two"
     }

  }
};


data.stuff = _.reject(data.stuff, function(val){
    return val.disabled;
});

data.stuff is now an array, rather than an Object. I've lost all my keys.

I have some data that I want to iterate through and reject those with a disabled: true property.

however when I try _.reject my object gets turned into an array.

var data = {
  stuff: {
     item1: {
        name: "one",
        disabled: true
     },
     item2: {
        name: "two"
     }

  }
};


data.stuff = _.reject(data.stuff, function(val){
    return val.disabled;
});

data.stuff is now an array, rather than an Object. I've lost all my keys.

• javascript
• underscore.js

• 1 _.reject can only return an array. – user229044 ♦ Commented Jan 5, 2014 at 7:50
• 1 Semantically, your stuff actually even should be an array. Really. item1, item2 either is useful data (then turn it into an id property, respectively) or it isn't (then drop it). – Tomalak Commented Jan 5, 2014 at 8:29

7 Answers 7

You could use _.omit() instead.

What @archie said but in code:

data.stuff = _.reduce(data.stuff, function(memo, value, key){
    if( !value.disabled) memo[key] = value;
    return memo;
}, {});

When you pass data.stuff (which is an Object) to _.reject, it picks only the values of the object and passes that to _.reject. So, key information is lost and reconstructing the object is not possible.

Instead, you can do it like this

data.stuff = _.object(_.filter(_.pairs(data.stuff), function(list) {
    return list[1].disabled;
}));

console.log(data);

Output

{ stuff: { item1: { name: 'one', disabled: true } } }

How it works

1. _.pairs converts the {key:value} pairs into [key, value] array.

2. _.filter filters the items whose disabled is a falsy value.

3. _.object converts the filtered [key, value] array into {key:value} pairs.

I ended up just using native javascript instead of underscore:

//remove disabled items
for ( var item in data.stuff ) {
    if ( data.stuff[item].disabled ) {
        delete data.stuff[item];
    }
}

Use _.omit():

_.omit(data.stuff, function(val) { return val.disabled; });

See fiddle: https://jsfiddle/ehbmsb5k/

Have you looked at doing this with _reduce, where the memo is a new hash, in which you merge the items( key, value pair) you need.

The original data.stuff is not changed when you use reject. But since you are assigning to the stuff key, the original data is lost.

_.reject is supposed to work on and return arrays. You could try this in order to acplish what you want:

_.each(Object.keys(data.stuff), function(val) {
    if (data.stuff[val].disabled)
        delete data.stuff[val];
});