Here is my code for javascript for this simple task:
Add the element if it is not in an array.
if(_.contains(this.types,type_id)){
var index = this.types.indexOf(type_id);
this.types.splice(index,1);
}
else{
this.types.push(type_id);
}
Is there a more efficient way to do this?
You could do it without a 3rd party library, this would be more efficient, like this. (this only removes the first instance of a value if found, not multiple)
Javascript
var a = [0, 1, 2, 3, 4, 6, 7, 8, 9],
b = 5,
c = 6;
function addOrRemove(array, value) {
var index = array.indexOf(value);
if (index === -1) {
array.push(value);
} else {
array.splice(index, 1);
}
}
console.log(a);
addOrRemove(a, b);
console.log(a);
addOrRemove(a, c);
console.log(a);
Output
[0, 1, 2, 3, 4, 6, 7, 8, 9]
[0, 1, 2, 3, 4, 6, 7, 8, 9, 5]
[0, 1, 2, 3, 4, 7, 8, 9, 5]
On jsfiddle
For immutable state ( clone array ):
const addOrRemove = (arr, item) => arr.includes(item) ? arr.filter(i => i !== item) : [ ...arr, item ];
lodash "xor" function_.xor([2, 1], [2, 3]);
// => [1, 3]
If you don't have an array as 2nd parameter you can simpy wrap the variable into an array
var variableToInsertOrRemove = 2;
_.xor([2, 1], [variableToInsertOrRemove]);
// => [1]
_.xor([1, 3], [variableToInsertOrRemove]);
// => [1, 2, 3]
Here's the doc: https://lodash.com/docs/4.16.4#xor
If you care about efficiency then may be using an array to implement a set is a bad idea. For example using an object you could do:
function toggle(S, x) {
S[x] = 1 - (S[x]|0);
}
then after many add/remove operations you can keep only keys where the value is 1
This way every addition/removal is O(1) and you need only one O(n) operation to get the final result.
If keys are all "small" numbers may be a bitmask is even worth the effort (not tested)
function toggle(S, x) {
var i = x >> 4;
S[i] = (S[i]|0) ^ (1<<(x&15));
}
Look at this answer of similar question.
Code:
function toggle(collection, item) {
var idx = collection.indexOf(item);
if (idx !== -1) {
collection.splice(idx, 1);
} else {
collection.push(item);
}
}
If "types" can be a Set then
let toggle = type_id => this.types.delete(type_id) || this.types.add(type_id);
Using underscorejs
function toggle(a,b)
{
return _.indexOf(a,b)==-1?_.union(a,[b]):_.without(a,b);
}
Usage:
var a = [1,2,3];
var b = [4];
a = toggle(a,b); // [1,2,3,4]
a = toggle(a,b); // [1,2,3]
Extending Xotic750's answer this will always ensure that toggled elements occur only once in array. You this if your arrays are bit random like user inputs.
function toggleValueInArray(array, value) {
var index = array.indexOf(value);
if (index == -1) {
array.push(value);
} else {
do {
array.splice(index, 1);
index = array.indexOf(value);
} while (index != -1);
}
}
var a = [0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9],
b = 5,
c = 10;
// toString just for good output
console.log(a.toString());
toggleValueInArray(a, b);
console.log(a.toString());
toggleValueInArray(a, c);
console.log(a.toString());