masautt

// Change the class altogether?
document.getElementById("MyElement").className = "MyClass";

// Add to the class?
document.getElementById("MyElement").className += "MyClass";

// Add or Remove a new class?
document.getElementById("MyElement").classList.add('MyClass');
document.getElementById("MyElement").classList.remove('MyClass');

masautt

var obj = { first: "John", last: "Doe" };

Object.keys(obj).forEach(function(key) {
    console.log(key, obj[key]); // first, John
                                // last, Doe
});

masautt

let obj = { key: undefined }

// Check if the key is defined (warning: key could exist but set to undefined)
obj["key"] !== undefined; //false, but key still exists

//Check if the key is defined in the object (includes if set to undefined)
"key" in obj; // true, regardless of actual value

//Check if the key doesn't exist?
!("key" in obj); // false

masautt

let obj = { key: undefined }

// Check if the key is defined (warning: key could exist but set to undefined)
obj["key"] !== undefined;

//Check if the key is defined in the object (includes if set to undefined)
"key" in obj;

//Check if the key doesn't exist?
!("key" in obj);

masautt

document.getElementById("myBtn").addEventListener("click", e => {
  //some code
  e.preventDefault(); //This specifically removes the default behavior of refreshing the page
})

masautt

let myArr = ["1", "2", "3"];

myArr.push("4");

console.log(myArr);

masautt

let str = "mylowercasestring";

let cappedStr = str.charAt(0).toUpperCase() + name.slice(1));

console.log(cappedStr); //--> "Mylowercasestring"

masautt

//Get the EPOCH Time
console.log(Date.now()) //--> 1567548304725

//Get a string date
console.log((new Date).toLocaleString()); //--> 9/3/2019, 3:07:03 PM

masautt

function genUUID() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  });
}

console.log(genUUID()) //--> 26a63d24-aef9-4047-9284-9fdb366bae95

masautt

let checkBox = document.getElementById("myCheckBox");

console.log(checkBox.checked) //--> true or false