How to remove undefined values from array but keep 0 and null

问题

In javascript, I want to remove undefined values, but keep the values 0 and null from an array.

[ 1, 2, 3, undefined, 0, null ]

How can I do it cleanly?

回答1:

You can use _.compact(array);

Creates an array with all falsey values removed. The values false, null, 0, "", undefined, and NaN are falsey.

See: https://lodash.com/docs/4.15.0#compact

回答2:

The best way using lodash is _.without

Example:

const newArray = _.without([1,2,3,undefined,0,null], undefined);

回答3:

No need for libraries with modern browsers. filter is built in.

    var arr = [ 1, 2, 3, undefined, 0, null ];
    var updated = arr.filter(function(val){ return val!==undefined; });
    console.log(updated);

回答4:

With lodash, you can do simply:

var filtered = _.reject(array, _.isUndefined);

If you also want to filter null as well as undefined at some point:

var filtered = _.reject(array, _.isNil);

回答5:

Using lodash, the following remove only undefined values from the array:

var array = [ 1, 2, 3, undefined, 0, null ];

_.filter(array, function(a){ return !_.isUndefined(a) }
--> [ 1, 2, 3, 0, null ]

Or, the following will remove the undefined, 0 and null values:

_.filter(array)
--> [1, 2, 3]

And if you want to remove null and undefined values from the array, but keep the values equal to 0:

_.filter(array, function(a){ return _.isNumber(a) || _.isString(a) }
[ 1, 2, 3, 0 ]

回答6:

You can try this one.

var array = [ 1, 2, 3, undefined, 0, null ];
var array2 = [];
for(var i=0; i<array.length; i++){
    if(!(typeof array[i] == 'undefined')){
        array2.push(array[i]);
    }
}
console.log(array2);

回答7:

Vanilla JS solution: By using ===, you can check if the value is actually undefined and not falsy.

Both snippets below will give you an array with [1, 2, 3, 0, null].

Both modify the original array.

// one liner - modifies the array in-place
[ 1, 2, 3, undefined, 0, null ].forEach( function(val, i, arr){
    if(val===undefined){arr.splice(i,1)}; // remove from the array if actually undefined
});

// broken up for clarity - does the same as the above
var myarray = [ 1, 2, 3, undefined, 0, null ];
myarray.forEach( function(val, i, arr){
    if(val===undefined){arr.splice(i,1)};// remove from the array if actually undefined 
});
console.log(myarray );

回答8:

Filter the given array for elements not equal to undefined.

const initialArray = [ 1, 2, 3, undefined, 0, null ];
const finalArray = initialArray.filter(element => element !== undefined);

回答9:

With ES6 Array#filter method

array.filter(item => item !== undefined)

回答10:

const finalArray = initialArray.filter(i => Boolean(i))

来源：https://stackoverflow.com/questions/39519440/how-to-remove-undefined-values-from-array-but-keep-0-and-null

标签

lodash