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The difference between find and filter in es6: 1, when looking for qualified contents in the array without changing the array, the result returned by the find method is the object, and the result returned by the filter method is the array; 2, if there is no value to meet the test function, the find method returns an undefined, and the filter method returns an empty array.

This tutorial operating environment: windows10 system, ECMAScript version 6. 0, Dell G3 computer.

What is the difference between find and filter in es6

1. Both find and filter are methods that do not change the original array, and both find the contents that meet the conditions in the array without changing the array. The difference is that find returns objects and filter returns arrays.

Examples are as follows:

Const list = [{'name':'1',index:1}, {' name':'2'}, {'name':'1'}] let list2 = list.find (I = > I. Nameplate examples examples 1') let list3 = list.filter (I = > I. Nameglasses examples examples 1') console.log (list); [{name:'1 indexname 1}, {name:'2'}, {name:'1'}] console.log (list2) {name: '1percent, index: 1} console.log (list3); [{name:' 1percent, index: 1}, {name:'1'}]

Find only finds the first qualified result, as in the example, an object is returned directly instead of an array! And filter returns that all the results are still arrays.

Note: find () will not traverse the following elements after finding the first element, so if there are two identical elements in the array, he will only find the first one and the second will not traverse again.

two。 To sum up, the query efficiency of find is more efficient, so it is best to use find if the data in the array is unique.

Find ()

The ES6 find () method returns the value of the first element that passes the test function. If no value satisfies the test function, undefined is returned.

Grammar

The arrow function used in the following syntax.

Find ((element) = > {/ *... * /}) find ((element, index) = > {/ *... * /}) find ((element, index, array) = > {/ *... * /})

Filter ()

The filter () method creates a new array containing all the elements that pass the test function. If no element satisfies the test function, an empty array is returned.

Grammar

Filter ((element) = > {/ *... * /}) filter ((element, index) = > {/ *... * /}) filter ((element, index, array) = > {/ *... * /})

Common point

Higher-order functions: both functions are higher-order functions.

Difference

1. Pass a test function

Find () returns the first element.

Filter () returns a new array of all elements that pass the test function.

2. If no value satisfies the test function

Find () returned undefined

Filter () returns an empty array

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