const numbers = [1, 2, 3]; // inferred to type number[]
numbers.push(4); // no error
// comment line below out to see the successful assignment
numbers.push("2"); // Error: Argument of type 'string' is not assignable to parameter of type 'number'.
console.log(numbers);
let head: number = numbers[0]; // no error
console.log(head);
prog.ts(4,20): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.