how to check if all object keys has false values

问题:

JS Object:

var saver = {
        title: false,
        preview: false,
        body: false,
        bottom: false,
        locale: false
};

The question is how to check if all values is false?

I can use $.each() jQuery function and some flag variable, but there may be a better solution?

回答1:

This will do the trick...

var result = true;

for (var i in saver) {
    if (saver[i] === true) {
        result = false;
        break;
    }
}

You can iterate objects using a loop, either by index or key (as above).

If you're after tidy code, and not repeating that then simply put it in a function...

Object.prototype.allFalse = function() { 
    for (var i in this) {
        if (this[i] === true) return false;
    }
    return true;
}

Then you can call it whenever you need, like this...

alert(saver.allFalse());

Here's a working sample...

Object.prototype.allFalse = function() { 
    for (var i in this) {
        if (this[i] === true) return false;
    }
    return true;
}

var saver = {
        title: false,
        preview: false,
        body: false,
        bottom: false,
        locale: false
};

console.log("all are false - should alert 'true'");
console.log(saver.allFalse());

saver.body = true;

console.log("one is now true - should alert 'false'");
console.log(saver.allFalse());

回答2:

In a comment you ask if you can avoid iteration. You can if you use a javascript library supporting a functional approach, like Underscore, Lodash or Sugar.

With Underscore and Lodash you can write something like this:

var result = _.every(_.values(saver), function(v) {return !v;});

With Sugar you can simply write:

var result = Object.all(saver,false);

回答3:

This is a very simple solution that requires JavaScript 1.8.5.

Object.keys(obj).every((k) => !obj[k])

Examples:

obj = {'a': true, 'b': true}
Object.keys(obj).every((k) => !obj[k]) // returns false

obj = {'a': false, 'b': true}
Object.keys(obj).every((k) => !obj[k]) // returns false

obj = {'a': false, 'b': false}
Object.keys(obj).every((k) => !obj[k]) // returns true

Alternatively you could write

Object.keys(obj).every((k) => obj[k] == false)
Object.keys(obj).every((k) => obj[k] === false)  // or this
Object.keys(obj).every((k) => obj[k])  // or this to return true if all values are true

See the Mozilla Developer Network Object.keys()'s reference for further information.

回答4:

If you want to do it without external iteration (i.e. in your code), try mapping the properties to an array with $.map then using $.inArray to see if any true values exist:

var allFalse = $.inArray(true, $.map(saver, function(obj){return obj})) < 0;

JSFiddle: http://jsfiddle.net/TrueBlueAussie/FLhZL/1/

回答5:

Do like this,

 for (var i in saver) {
  if (saver[i]) {
    return false; // here if any value is true it wll return as false /
  }
 }
 return true; //here if all value is false it wll return as true

回答6:

As of Lodash 4.0, overEvery can be used

overEvery(saver, false) loops through every element & checks if its false

It returns true if every element is false otherwise returns false

回答7:

Short and handy one-liner, fully supported by browsers:

Object.keys(saver).every(k => saver[k] === false);

or

Object.values(saver).every(v => v === false);

(careful tho, Object.values() is not supported by IE yet.)

回答8:

With lodash you could also do const result = _.some(saver);