how to get a property dinamically from an object javascript code example

Example 1: javascript dynamically access object property

var person ={"first_name":"Billy","last_name":"Riley"};
var property_name="first_name";
alert(person[property_name]); //Dynamically access object property with bracket notation

Example 2: nodejs how to use dynamic variable after dot

model.car // static way

const myDynamicVariable = 'car'
model[myDynamicVariable] // works like model.car - here you can dynamicly use a variable after dot