push to deepest child with spread js code example

Example 1: ellipsis javascript

/* Spread syntax ( ex. ...arrayName) allows an iterable such as an array expression or string 
to be expanded in places where zero or more arguments (for function calls) 
elements (for array literals) are expected, or an object expression to be 
expanded in places where zero or more key-value pairs (for object literals) 
are expected. */


//example
function sum(x, y, z) {
  return x + y + z;
}

const numbers = [1, 2, 3];

console.log(sum(...numbers));
// expected output: 6

Example 2: javascript spread operator

function myFunction(v, w, x, y, z) { }
let args = [0, 1];
myFunction(-1, ...args, 2, ...[3]);