[英]Why isn't this recursion working on Javascript?
The problem is in the listToArray function, arrayToList just there to provide context on how lists are being created. 问题出在listToArray函数中,其中的arrayToList提供了有关如何创建列表的上下文。
var arrayToList = function (array) {
var lastList = null;
for (i=array.length-1; i >= 0; i--) {
var list = {value : array[i], rest : lastList};
lastList = list;
}
return lastList;
}
var list = arrayToList([1,2,3])
var listToArray = function (list) {
var array = [];
array.push(list.value);
if (list.rest != null) {
array.concat(listToArray(list.rest));
} else {
return array;
}
}
var array = listToArray(list)
> list
{ value: 1, rest: { value: 2, rest: { value: 3, rest: null } } }
> array
undefined
Couple of fixes : 几个修复 :
array.concat
必须返回要在array.concat
使用的array.concat
arr = []
loses the context of the previous. 每当新的arr = []
失去上一个的上下文时。 Either it should be passed as a parameter, or keeping it in a global context. 要么将其作为参数传递,要么将其保留在全局上下文中。 Run the following snippet. 运行以下代码段。
var arrayToList = function(array) { var lastList = null; for (i = array.length - 1; i >= 0; i--) { var list = { value: array[i], rest: lastList }; lastList = list; } return lastList; } var list = arrayToList([1, 2, 3]) var listToArray = function(list, array) { if (!array) { array = []; } array.push(list.value); if (list.rest != null) { array.concat(listToArray(list.rest, array)); } else { return array; } // need to return the array which is used in array.concat return array; } var array = listToArray(list); console.log(list); console.log(array);
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