JavaScript Programming Questions

From Manfredhu Blog: http://www.manfredhu.com/2016/04/02/15-veryGoodForUsing/

1. Use reduce to count the number of distinct words in an array

var  arr = [ Span class= "hljs-string" > "Apple" ,  "Orange" , , , " pear ", " Orange "]; function  getWordCnt   ()  { return  arr.reduce (function   (Prev,next,index,arr  { Prev[next] = (Prev[next] + 1 ) | | 1 ;    //This sentence is the focus   return  prev; },{});} Console.log (getwordcnt ());  

2. Given the string str, check whether it contains consecutive duplicate letters (A-ZA-Z), which contains true, otherwise returns false

function containsRepeatingLetter(str) {     return/([a-zA-Z])\1/// \1指代第一个括号的匹配项}

In regular expressions, you use () to group, use slashes and numbers to denote references, \1 refers to the first grouping, and \2 refers to the second grouping. by making [a-za-z] a grouping, and then referencing, you can determine whether there is a continuous repetition of the letters.

3. The FN is known as a pre-defined function that implements the function Curryit

Code that needs to be fully complementary

varfunction(a, b, c) {    return a + b + c};curryIt(fn)(1)(2)(3//6function curryIt(fn) {    //这里补充}

Try to play, here is the function of the currying

varfn = function(A, B, c) {    returnA + B + c};console.log (Curryit (FN) (1)(2)(3));//6 function curryit(fn) {    varlen = fn.length;//Get the number of function parameters    varSlice =Array. Prototype.slice;vararg = Slice.call (arguments,1);return  function() {arg = Arg.concat (Slice.call (arguments));if(Arg.length < Len) {called when equal to the number of parameters required by the function            return arguments. callee; }Else{returnFn.apply (NULL, ARG); }    }}

JavaScript Programming Questions