settimeout syntax in javascript explain code example

Example 1: for of loop syntax javascript

for (let step = 0; step < 5; step++) {
  // Runs 5 times, with values of step 0 through 4.
  console.log('Walking east one step');
}

Example 2: syntax of reduce in js

[1,2,3,4,5].reduce((acc, current)=>acc+current, 0)