实现全排列

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function permutate(str) {       var result=[];     if(str.length==1){         return [str]        }else{                   var preResult=permutate(str.slice(1));             for (var j = 0; j < preResult.length; j++) {                 for (var k = 0; k < preResult[j].length+1; k++) {                     var temp=preResult[j].slice(0,k)+str[0]+preResult[j].slice(k);                                  result.push(temp);                              }             }         return result;       }  }   console.log(permutate("abc"));     https://www.cnblogs.com/star91/p/5615327.html