Array algorithm telephone number combination

Given a string containing only 2-9, it can return all letter combinations indicated. Letters to numbers given map (FIG). Note that a letter does not correspond to any

 

 

Input: '23 '

Output: [ 'ad', 'ae', 'af', 'bd', 'be', 'bf', 'cd', 'ce', 'cf']

Law: 2 a count, makes up one, and continues to the next count, makes up 2, until the last

 

 

 

Code

Export default (STR) => {
     IF (! STR) return ;
     // establish a telephone number keypad mapping 
    let strMap = [ '', ' ', 'abc', 'def', 'ghi', 'jkl', 'mno ',' PQRS ',' TUV ',' wxyz ' ];
     // input a string of characters separated by a single array becomes, = 234> [2,3,4] 
    the let NUM = str.split (' ' );
     // character content after storage keyboard mapping, such as = 23 is> [ 'ABC', 'DEF] 
    the let code = []; 
    num.forEach (Item => {
         IF (strMap [Item]) { 
            code.push(strMap[item])
        }
    })

    let comb = (arr) => {
        //The temporary variable to store the results of the first two combinations of 
        the let TEMP = [];
         // outermost loop is traversing the first element, layer is a circle of a second element traversed 
        for (I = 0 the let, IL = ARR [0] .length; I <IL; I ++ ) {
             for (J = 0 the let, ARR JL = [. 1] .length; J <JL; J ++ ) { 
                temp.push ( `$ {ARR [ 0] [I ]} $ {ARR [. 1 ] [J]} `); 
            } 
        } 
        arr.splice ( 0, 2 , TEMP);
         IF (arr.length>. 1 ) { 
            COMB (ARR); 
        } the else {
             return TEMP; 
        } 
        return ARR [0 ]; 
    }
    return comb(code);
}

 

Summarize knowledge

Array.prototype.splice