General JS

js functions index

Boolean(any)
arr.find()
Number()
arr.every()
str.startsWith()
str.endsWith()

Notes

• arr.pop() and arr.unshift() returns the single Elemnt that they worked on.
• if you are returning a single element from an array, use arr.find() instead of arr.filter()

make a new promise

function sleep(ms = 0) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

//get the result after a second
sleep(1000).then((data) => console.log("data", data));

this and that

• this and that in js, that refering to the main this in a scope, while you are going deeper into a scope this will refer to the deeper element, while that will refer to the parent:

function MyConstructor(options) {
  let that = this;

  this.someprop = options.someprop || "defaultprop";

  document.addEventListener("click", (event) => {
    alert(that.someprop);
  });
}

new MyConstructor({
  someprop: "Hello World",
});

swap quickly

  x = 1;  y = 240;
  [x,y] = [y,x]
  >>> x, y  // 240 , 1

double ‘!!’

• we can use double exclamation points !! to get a boolean value from non-boolean:

let x = "abc"; // x is truthy;  !x = false; !!x = true;
let y = null; // y is falsey; !y = true; !!y= false;

show Nice json

 <pre>
    {JSON.stringify(values, null, 2)}
  </pre>