Underscorejs _.find (list, predicate, [context])

Grammar:

_.find (list, predicate, [context])

Description

Matches each member of the list collection sequentially (based on the predicate iteration function detection), and returns the current member immediately if the match succeeds

• List can be arrays, objects, strings, and arguments
• Predicate will pass the third parameter value, key, list (parameter name can be customized)
• predicate function needs return value
• Context can change the inside of the predicate function this

Code example: Example one: Find Array, object, string, arguments, and return matching successful data

varresult;//manipulating Arraysresult = _.find ([1, 2, 3],function(value) {returnValue = = 2;}); Console.log (Result)//= 2        //manipulating Objectsresult = _.find ({one: ' A ', two: ' II ', three: ' Three '},function(value) {returnValue = = = ' two ';}); Console.log (Result)//= "Two"//manipulating Complex objectsvarobj ={levela: {level0:' Level0 ', Level1:' Level1 '}, Levelb:A, LEVELC:1}result= _.find (obj,function(value) {returnValue.level0 = = = ' Level0 ';}); Console.log (Result)//= = Object {level0: "Level0", Level1: "Level1"}//Action String (here the character is split into an array)result = _.find (' 123 ',function(value) {returnValue = = = ' 2 ';}); Console.log (Result)//= "2"//Operation ArgumentsfunctionABC () {Result= _.find (arguments,function(value) {returnValue = = 2;    }); Console.log (result); //= 2}ABC (1, 2, 3);

Example two: Parameters passed by the predicate function (return return value is required inside the function, otherwise undefined)

varresult;//the case of an arrayresult = _.find ([1, 2, 3],function(value, key, list) {Console.log (value, key, list); //= 1 0 [1, 2, 3]    //= 2 1 [1, 2, 3]    //= 3 2 [1, 2, 3]    return true;//true to return the first member directly});//the case of the objectresult = _.find ({one: ' A ', two: ' II ', three: ' Three '},function(value, key, list) {Console.log (value, key, list); //= = One Object {one: "A", Two: "II", Three: "Three"}    //= Two two Object {one: "I", "II", Three: "Three"}    //= Three three Object {one: "A", Two: "II", Three: "Three"}    return true;//true to return the first member directly});

Example three: Context can change the internal predicate this

varresult;//the case of an arrayresult = _.find ([1, 2, 3],function(value, key, list) {Console.log ( This);//= = [1, 2, 3] This is an array}, [1, 2, 3]);//the case of the objectresult = _.find ([1, 2, 3],function(value, key, list) {Console.log ( This);//= = Object {No:10} This is a}, {"No": 10 });//case of a stringresult = _.find ([1, 2, 3],function(value, key, list) {Console.log ( This);//= = string {0: "1", 1: "2", 2: "3", Length:3, [[Primitivevalue]]: "123"} This is the object after the string has been split}, "123");

The _.detect function is the same as the _.find.

var function (value, key, list) {    return value = == 2//=2

Special case Example One: special case of List

// For example: Null,undefined,0,true,this etc; var result = _.find (nullfunction  (value, key, list) {    returnTrue //= "undefined"  

Example two: The case of the predicate function that is the window global object

// Example: null,undefined,window,this, etc. var function (value, key, list) {    Console.log (this//= = This is the window global object null) ;

Can the list parameter be a true or false value?

var  result = _.find ([falsetruenull//= = [1]

predicate have other written wording? Example one: When the predicate parameter is empty

var  result = _.find ({x:1, y:2//== [1]

Example two: When the predicate parameter is a single character

var  result = _.find ([{x:1}, {y:2}], ' x '//= = [{x:1}]

Example three: When the predicate parameter is an object

var obj = [    1, Y:2},    1},    2, Z:3}]var  result = _ . Find (obj, {x:1//= = [{x:1, y:2}]

Underscorejs _.find (list, predicate, [context])