Today I Learned

Javascript

Regex

pattern - /pattern/

flags - g (global) -> /pattern/g

Shortcuts:

• \d - any digit [0-9]
• \s - whitespace
• \w - word character [a-zA-Z0-9_]

Quantifiers:

• (-) - one or more
• (*) - zero or more

Strings

Removing whitespace

"hello world".replace(/ /g, ""); // output - helloworld using regex

"hello world".replaceAll(" ", ""); // output - helloworld, similar to regex

"hello world".split(" ").join(""); // output - helloworld

Loop

const fruit = "cat";
for (const c of fruit) {
  console.log("single character", c);
}

/* Output
single character c
single character a
single character t */

Join

const c = ["c", "a", "t"];
c.join(""); // cat

Arrays

const numArr = [1, 2, 3];

// Replace classical for loop

for (let val of numArr) {
  console.log(val); // 1,2,3
}

reduce method

// finding sum using reduce
[1, 2, 3].reduce((acc, currVal) => acc + currVal); // 1+2+3 = 6

TypeScript

Type safety on Objects

The below means, this object can have any string as a key and output will be a string.

const lookUp: { [key: string]: string } = {
  A: "T",
  T: "A",
  C: "G",
  G: "C",
};