questions 2

Question 1

Could you explain ““this”” in js?
What will ““this”” be equal?
And if we are in a nodeJS environment?

Answer 1

the global object in NodeJs will be .process instead of .window

Question 2

How to redefine ‘this’?

Answer 2

call, apply, bind

Question 3

What is a function in JavaScript?

Answer 3

All functions in JavaScript are objects. They are the instances of the Function type. Since functions are objects, they have properties and methods like other objects.

Question 4

What is a closure?

Answer 4

my answer + JS tries to find variable in local scope and if not then it tries to find var inside upper scope

Question 5

for(var i = 0; i < 10; i++) { setTimeout(function() {
console.log(i); }, 1000);
}
Could you explain this example? Could you fix this one?

Answer 5

use let, because of how var works inside the block scope(it resigning every iteration). when we use a let keyword our scope is running correctly inside of it.

Question 6

var x = 5; var obj = { x: 10,
doIt: function doIt(){ var x = 20;
setTimeout(function(){ console.log(this.x);
}, 10); }
};
function time() { console.log(this.x)
} obj.doIt();

Answer 6

5 because setTimeout function here has a global object .window as a context

Question 7

var funcs = [];
for (var i = 0; i < 3; i++) {
  funcs[i] = function() {
    console.log("My value: " + i); 
  };
}

for (var j = 0; j < 3; j++) { 
  funcs[j]();
}

Answer 7

3 times, returns 3 because of var keyword and how it works inside the block scope(it resigning every iteration) if we use let it will return us the correct values.

Question 8

Write function sum console.log(sum(1)(2)(3)); // 6

Answer 8

function a(x) {return function(y){return function(z){return x + y + z}}}

Question 9

How does js engine understand that this is a function?

Answer 9

because we call them in the moment when we call them

Question 10

Please, write the function that receives several arrays and finds the maximum value in all of them.

Answer 10

function a (...arrays) { -> rest syntax
  let max = -Infinity;
  arrays.forEach((arr) => {
    const arrMax = Math.max(...arr); -> spred syntax
    if(max < arrMax) {
      max = arrMax;
    }
  });
  return max;
}
undefined
a([1, 35, 67], [5, 99, 45], [120]);
120
'function b(...arrays) -> arrays = [arr1, arr2, arr3, arrn]'
"function b(...arrays) -> arrays = [arr1, arr2, arr3, arrn]"
`arr - [1,2,3,4, n], Math.max(...arr) -> Math.max(1,2,3,4, n)`
"arr - [1,2,3,4, n], Math.max(...arr) -> Math.max(1,2,3,4, n)"
Infinity
Infinity
Infinity > 99999999999999999999999
true
-Infinity < -99999999999999999999999
true