javascript按值在嵌套对象/数组深处查找

Question

hello , I have a problem returning an object in my function, Let's say I have an object:

var elements = [{
    "fields": null,
    "id_base": "nv_container",
    "icon": "layout",
    "name": "container",
    "is_container": true,
    "elements" : [
        //another elements set here
    ]
}, 
{
    "id_base": "novo_example_elementsec",
    "name": "hello",
    "icon": "edit",
    "view": {}
}];

what i want is a function (in pure javascript) that can find an object with a specific key and value , and i have created a function but its just not working fine ? , my function :

function findNested(obj, key, value) {
    //Early return
    if (obj[key] === value) {
        console.log( 'before return' ); //until here . its fine
        return obj; //not working
    } else {
        for (var i = 0, len = Object.keys(obj).length; i <= len; i++) {
            if (typeof obj[i] == 'object') {
                this.findNested(obj[i] , key, value);
            }
        }
    }
}

I just can't see what I've done wrong ?

thanks.

Answer 1

You're missing a return after making the recursive call. If the object is found after recursing, you need to continue to bubble that result up (by returning it). You should also be using i < len (not i <= len ) as pointed out by @scott-marcus.

 var elements = [{ "fields": null, "id_base": "nv_container", "icon": "layout", "name": "container", "is_container": true, "elements": [ //another elements set here ] }, { "id_base": "novo_example_elementsec", "name": "hello", "icon": "edit", "view": {} } ]; function findNested(obj, key, value) { // Base case if (obj[key] === value) { return obj; } else { for (var i = 0, len = Object.keys(obj).length; i < len; i++) { if (typeof obj[i] == 'object') { var found = this.findNested(obj[i], key, value); if (found) { // If the object was found in the recursive call, bubble it up. return found; } } } } } console.log(findNested(elements, "icon", "layout")); // returns object console.log(findNested(elements, "icon", "edit")); // returns object console.log(findNested(elements, "foo", "bar")); // returns undefined 

Answer 2

Just for future readers. Additionally to @user94559 answer.

1. A more generic way would be to iterate over the keys instead of the indices , otherwise not all nested properties will found.
2. And check obj[k] before making the recursion call to ignore null values

 var elements = [{ "fields": null, "id_base": "nv_container", "icon": "layout", "name": "container", "is_container": true, "elements": [ {"icon": "nested"} ] }, { "id_base": "novo_example_elementsec", "name": "hello", "icon": "edit", "view": {} } ]; function findNested(obj, key, value) { // Base case if (obj[key] === value) { return obj; } else { var keys = Object.keys(obj); // add this line to iterate over the keys for (var i = 0, len = keys.length; i < len; i++) { var k = keys[i]; // use this key for iteration, instead of index "i" // add "obj[k] &&" to ignore null values if (obj[k] && typeof obj[k] == 'object') { var found = findNested(obj[k], key, value); if (found) { // If the object was found in the recursive call, bubble it up. return found; } } } } } console.log(findNested(elements, "icon", "layout")); // returns object console.log(findNested(elements, "icon", "edit")); // returns object console.log(findNested(elements, "foo", "bar")); // returns undefined // this will work now console.log(findNested(elements, "icon", "nested")); // returns object