javascript - Check if object exists in an array before pushing - Stack Overflow

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I have an empty array and a selectable tree, and every time when the user is checking or un-checking a node I'm pushing the node's id and if the checkbox is true or false.

But right now if the user will check and then un-check a node there will be two objects in the array of the same node how can i make sure that doesn't happen?

//creating empty array

var checkedItems = []; 

//(in kendo observable) on user selection I'm pushing the checked node to array

onItemChecked : function (e) {
    var node = e.sender.dataItem(e.node);
    checkedItems.push({Id: node.Id, IsChecked: node.checked});
},

I have an empty array and a selectable tree, and every time when the user is checking or un-checking a node I'm pushing the node's id and if the checkbox is true or false.

But right now if the user will check and then un-check a node there will be two objects in the array of the same node how can i make sure that doesn't happen?

//creating empty array

var checkedItems = []; 

//(in kendo observable) on user selection I'm pushing the checked node to array

onItemChecked : function (e) {
    var node = e.sender.dataItem(e.node);
    checkedItems.push({Id: node.Id, IsChecked: node.checked});
},

• javascript
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Share Improve this question Follow edited Jul 5, 2016 at 21:11 ManoDestra 6,50366 gold badges2929 silver badges5050 bronze badges asked Jul 5, 2016 at 20:58 agDevagDev 86511 gold badge1111 silver badges2020 bronze badges

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3 Answers 3

Sorted by: Reset to default 6

You can, before pushing a new object, check the presence of an object that has that id.

var el = checkedItems.filter(function(el) {
    return el.Id === node.Id;
});

if (el.length) {
    el[0].IsChecked = node.checked;
} else {
   // push a new object
}

You can just use an object, which is guaranteed to have unique keys:

var checkedItems = {};
onItemChecked : function (e) {
    var node = e.sender.dataItem(e.node);
    checkedItems[node.Id] = node.checked;
},

You have a Id which is grate, cuz that can be used for uniqueness. So maybe an array is not the best suited for what you want to acplish. There are better way to handle it with just plain object (see Mike McCaughan answer) and Map

var items = new Map
items.set(node.Id, node.checked)

// Removing items is as easy as 
items.remove(node.Id)

// Getting
var checked = items.get(node.Id)

// Then if you want to iterate over them you would do something like:
for (var [key, value] of items.entries()) {
    console.log(key + " = " + value)
}

var values = items.values()
var keys = items.keys()

Map's are like a key/value storage, much like object

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