17. 电话号码的字母组合.js

var letterCombinations = function(digits) {
    if(digits == ''){
        return []
    }
    var map = ['',1,'abc','def','ghi','jkl','mno','pqrs','tuv','wxyz']
    var code = digits.split('').map(e => map[e])
    function combine(arr) {
        if(arr.length == 1){
		    return arr[0].split('')
	    }
        let result = []
        for(let n of arr[0]){
            for(let m of arr[1]){
                result.push(n+m)
            }
        }
        arr.splice(0,2,result)
        if(arr.length > 1){
            combine(arr)
        }else{
            return result
        }
        return arr[0]
    }
    return combine(code)
};


console.log(letterCombinations('234'))