Array aspect JS bottom code learning record

I. Clear () →array

function Clear () {            this. length = 0;              return  This ;        }

Returns an empty array that clears item.

Example:

var fruits = [' Apple ', ' Orange ', ' Bananas ', ' Peach '];fruits.clear (); // , [] Fruits // , []

　　

Two. Clone () →array

  function Clone () {    return slice.call (this, 0);  }

Returns a copy of the array, keeping the original array intact.

Iii. Compact ()　→array

  function Compact () {    returnthis. Select (function(value) {      return  null;    });  }

Returns a copy that does not contain null and undefined

Example:

var null, ' C '); var copy = orig.compact (); // orig, [Undefined, ' A ', Undefined, ' B ', null, ' C ']; // copy---[' A ', ' B ', ' C '];

　Iv. every ([iterator = prototype.k[, context]) →boolean

• iterator ( Function ) -An optional function to evaluate each element in the enumeration; The function should return a value to test. If not provided, the element itself is tested.
• context ( Object ) - An optional object that is used in a this call to an iterator .

Determines whether all elements are true (boolean-equivalent true), calculated either directly or through the provided iterator. (I can't quite understand this one.)

 functionevery (iterator) {if( This==NULL)Throw NewTypeError (); Iterator= Iterator | |PROTOTYPE.K; varcontext = Arguments[1]; varObject = Object ( This);  for(vari = 0, length = object.length >>> 0; i < length; i++) {      if(IinchObject &&!Iterator.call (context, object[i], I, object)) {        return false; }    }    return true; }  if(arrayproto.every) {every=wrapnative (Array.prototype.every); }

　　V.. filter (iterator[, context]) →array

• iterator ( Function ) -An iterator function that is used to test the element.
• context ( Object )  - this An optional object that is used in a call to an iterator .

returns a new array containing all the items in this array, where iterator returns a truth value.

 functionFilter (iterator) {if( This==NULL|| !object.isfunction (iterator))Throw NewTypeError (); varObject = Object ( This); varresults = [], context = Arguments[1], value;  for(vari = 0, length = object.length >>> 0; i < length; i++) {      if(Iinchobject) {Value=Object[i]; if(Iterator.call (context, value, I, object)) {Results.push (value); }      }    }    returnresults; }  if(arrayproto.filter) {//' Array#filter ' requires an iterator by nature, so we don ' t need to    //Wrap it.Filter =Array.prototype.filter; }

　　Vi.. First ()

  function First () {    returnthis [0];  }

　　returns the first item of an array (for example, array[0] ).

　　Vii.. Flatten () →array

function Flatten () {    returnthisfunction(array, value) {      if (Object.isarray (value))         return Array.concat (Value.flatten ());      Array.push (value);       return array;    });  }

Personal understanding: Merges all arrays within the specified array.

Official Understanding:

returns a flat (one-dimensional) copy of the array, keeping the original array intact. nested arrays are injected recursively inline.

Commonly used in processing the results of recursive collection algorithms.

Example:

var a = [' Frank ', [' Bob ', ' Lisa '],[' Jill ', [' Tom ', ' Sally ']] ; var b = a.flatten (); // a   // b  -> [' Frank ', ' Bob ', ' Lisa ', ' Jill ', ' Tom ', ' Sally ']

Viii.. IndexOf (item[, offser = 0]) →number

 functionindexOf (item, i) {if( This==NULL)Throw NewTypeError (); varArray = Object ( This), length = Array.Length >>> 0; if(length = = 0)return-1; //The rules for the ' fromIndex ' argument is tricky. Let ' s follow the    //spec Line-by-line.i =Number (i); if(IsNaN (i)) {i= 0; } Else if(I!== 0 &&isfinite (i)) {      //equivalent to ES5 ' s ' tointeger ' operation.i = (i > 0? 1:-1) *Math.floor (Math.Abs (i)); }    //If The search index is greater than the length of the array,    //return-1.    if(i > Length)return-1; //If The search index is negative and take its absolute value, subtract it    //From the length, and make the new search index. If it ' s still    //negative, make it 0.    vark = i >= 0? I:math.max (Length-math.abs (i), 0);  for(; k < length; k++)      if(kinchArray && array[k] = = = Item)returnK; return-1; }

Official Understanding:

• item( ? ) -values that might or may not exist in the array.
• offset( Number ) -the number of initial items to skip before starting the search.

Returns the first occurrence of an index in the item array, or 1 if item does not exist in the array. Array#indexof uses absolute equals (= = =) to compare items.

Personal understanding: Returns the index of the position where item first appears in the array, because it distinguishes between the use of absolute equals so case-sensitive, type.

Example:

[3, 5, 6, 1, 20].indexof (1)// -- 3 [3, 5, 6, 1, 20].indexof (+)//  -> ; -1 (not found) [' 1 ', ' 2 ', ' 3 '].indexof (1); // -1 (not found, 1!== ' 1 ')

Add an example that is not an array:

var str= "Hello world!" document.write (Str.indexof ("Hello") + "<br/>") document.write (Str.indexof("World") + "< br/> ") document.write (Str.indexof (" World "))//  ->0//  ->- 1//  ->6

　　Ix.. Inspect () →string

function Inspect () {    returnthis. Map (object.inspect). Join (', ') + '] ';  }

Returns a debug-oriented string representation of an array.

Example:

[' Apples ', {good: ' Yes ', bad: ' No ', 3,].inspect () // "[' Apples ', [Object Object], 3,"] "

X.. Intersect (Array) →array

  function intersect (array) {    returnthis. Uniq (). FindAll (function(item) {       return array.indexof (item)!==-1;    });  

Returns an array of each of the same items that are contained in two of a given array.

Array aspect JS bottom code learning record