Vuejs Watch On Array

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You should pass an object instead of boolean as options, so:. Or you could set the watcher into the vue instance like this:.

If someone needs to get an item that was changed inside the array, please, check it:.

JSFiddle Example. The post example code:. You can watch each element in an array or dictionary for change independently with $watch('arr.0', () => {}) or $watch('dict.keyName', () => {}).

Overview #

from https://vuejs.org/v2/api/#vm-watch:. Note: when mutating (rather than replacing) an Object or an Array, theold value will be the same as new value because they reference thesame Object/Array.

Vue doesn’t keep a copy of the pre-mutate value.

However, you can iterate the dict/array and $watch each item independently. $watch('foo.bar') - this watches changes in the property 'bar' of the object 'foo'.

In this example, we watch all items in arr_of_numbers, also 'foo' properties of all items in arr_of_objects:.

BREAKING: When watching an array, the callback will only trigger when the array is replaced. If you need to trigger on mutation, the deep option must be specified.

When using the watch option to watch an array, the callback will only trigger when the array is replaced.

In other words, the watch callback will no longer be triggered on array mutation. To trigger on mutation, the deep option must be specified. If you rely on watching array mutations, add the deep option to ensure that your callback is triggered correctly.

Vue.js provides the watch option for responding to changes in data.

By default, when working with an array of objects, a watch object’s handler function is only triggered by mutations to the array itself and not the values of the object properties.

Turning to the docs, in order to detect nested value changes in objects you need to set the watch object’s deep property to true as shown below:.