How to get child object's element? [duplicate]

问题:

This question already has an answer here:

• How can I access and process nested objects, arrays or JSON? 22 answers

How to get e's value without knowing which group, which means only use obj and e?

And also can use same way to get a.

Thanks

let obj:Object = {
  a: 'value1',
  b: 'value2',
  group1: {
    c: 'value3',
    d: 'value4'
  },
  group2: {
    e: 'value5',
    f: 'value6'
  }
};

回答1:

I would do it like this:

function findValue(key, obj) {
    for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
            if (i === key) {
                return obj[i];
            } else if (typeof(obj[i]) == "object") {
                var value = findValue(key, obj[i]);
                if (typeof(value) !== "undefined") { return value; }
            }
        }
    }
}

findValue('a', obj);
//"value1"
findValue('e', obj);
//"value5"

回答2:

You can use Object.keys() to iterate through properties and Object.hasOwnProperty() to test if object contains property:

let key = Object.keys(obj)
                .find(k => obj[k].hasOwnProperty('e'));

console.log(obj[key].e);

回答3:

Version which returns falsy values, too.

function find(key, object) {
    var value;
    Object.keys(object).some(function (k) {
        if (key === k) {
            value = object[k];
            return true;
        }
        if (typeof object[k] === 'object') {
            value = find(key, object[k]);
            return value !== undefined;
        }
    });
    return value;
}

var obj = { a: 'value1', b: 'value2', group1: { c: 'value3', d: 'value4' }, group2: { e: 'value5', f: 'value6' }, group3: { g: '', h: 0 } };

document.write(find('e', obj) + '<br>');
document.write(find('g', obj) + '<br>');
document.write(find('h', obj) + '<br>');