my code is like that. it was work at first.. not more
function HA7(arr, id) {
for (let i = 0; i < arr.length; i++) {
if(arr[i]['id']=== id) {
return arr[i]
}
else if(arr[i]=== undefined && arr[i][id] === id ) {
return arr[i][id]
}
else if(arr[i][id] === undefined){
return null ;
}
return HA7(arr[i],id)
}
}
I wanna more continue work by recursive function .. but once agian only return null. (i wanna catch case id value null or arr is undefined)
// example code.
let arr = [
{
id: 1,
name: 'johnny',
},
{
id: 2,
name: 'ingi',
children: [
{
id: 3,
name: 'johnson',
},
{
id: 5,
name: 'steve',
children: [
{
id: 6,
name: 'lisa',
},
],
},
{
id: 11,
},
],
},
{
id: '13',
},
];
let output = HA7(arr, 1);
console.log(output); // --> { id: 1, name: 'johnny' }
output = HA7(arr, 5);
console.log(output); // --> { id: 5, name: 'steve', children: [{ id: 6, name: 'lisa' }] }
output = HA7(arr, 99);
console.log(output); // --> null
How should I fix it more? please tell me a some tips ..
transformation 1
Replacing for(;;) loop with for..of -
function HA7(arr, id) {
for (const x of arr) {
if(x.id === id) {
return x
}
else if(x=== undefined && x[id] === id ) {
return x[id]
}
else if(x[id] === undefined){
return null
}
return HA7(x,id)
}
}
It's much easier to see what's going on, thanks to replacing all arr[i] with a simple x. We also changed x["id"] to a simple x.id. Now we can see other problems.
You are testing x.id and x[id] before checking if x is null or undefined.
You make a check like x === undefined && x[id] === id that will always be false. This is because if x is undefined, the && x[id] will not only be false, it will also throw an error because you are trying to lookup a property an a null object
You are writing x[id] where you probably mean to write x.id
You are writing return null before we have exhausted the search
transformation 2
Let's fix all of the problems we identified above -
function HA7(arr, id) {
for (const x of arr) {
if (x == null) // <- check nulls first, always
continue // <- don't return yet
else if (x.id == id) // <- or when id matches
return x // <- return x
else // <- otherwise
for (const child of HA7(x.children, id)) // <- search children
if (result != null) // <- if result is found
return result // <- return it
}
}
transformation 3
Using generators we can do this even better -
function* HA7 (arr, id)
{ for (const x of arr)
{ if (x == null) continue
if (x.id == id) yield x
if (x.children) yield *HA7(x.children, id)
}
}
function first (t)
{ for (const x of t)
return x
}
const input =
[{id: 1,name: 'johnny'},{id: 2,name: 'ingi',children: [{id: 3,name: 'johnson'},{id: 5,name: 'steve',children: [{id: 6,name: 'lisa'},],},{id: 11},],},{id: '13'}]
console.log(first(HA7(input, 1)))
console.log(first(HA7(input, 5)))
console.log(first(HA7(input, 99))){
"id": 1,
"name": "johnny"
}
{
"id": 5,
"name": "steve",
"children": [
{
"id": 6,
"name": "lisa"
}
]
}
undefined
I just wrote an post that is very similar to this question. Please see this Q&A for additional explanation and other advantages of using generators for this kind of problem.
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