Angular 2 get key and value from json array with dynamic key

In your example, you have an array of objects and each of these object has exactly one property.

for (let obj of arr) {
    console.log("object:", obj);
    for (let key in obj) {
        console.log("      key:", key, "value:", obj[key]);
    }
}

The following code from your posting

for (let key in arr) {
    console.log ('key: ' +  key + ',  value: ' + arr[key]);
}

... would work on a data structure like this:

let arr = {
    key1: 'val1',
    key2: 'val2',
    key3: 'val3'
};

If you are more concerned to specify object like

var temp={'name':Dinesh,'age':18}

You may use following syntax.

console.log(Object.keys(temp)[0],Object.values(temp)[0]):

Specially zero index because object's both method keys and values return an array

You need another for loop to access key and value,

for (let key of this.arr) {
 for(var i in key){
      console.log('key: ' +  i + ',  value: ' + key[i]);
 }
}

Check the console

DEMO