JavaScript Strings
المعرفة:: JavaScript
الحالة:: ملاحظة_مؤرشفة
المراجع:: The Complete JavaScript Course 2022 From Zero to Expert, syahshiimi’s notes, syahshiimi’s notes, syahshiimi’s notes
How string methods work?¶
Whenever we call a method on a string, JavaScript will convert that string primitive to string object with same content using new String(), that object has all string methods, and when the process is done, the object is converted back to a regular string primitive. This process is called boxing.
Getting character of a string in a specific position¶
const plane = "A320";
console.log(plane[0]); // A
console.log(plane[1]); // 3
console.log(plane[2]); // 2
console.log("B737"[0]); // B
String Length¶
const airline = "TAP Air Portugal";
console.log(airline.length); // 16
console.log("B737".length); // 4
Getting the position of a certain letter in a string¶
const airline = "TAP Air Portugal";
// getting the index of specific alphabet
console.log(airline.indexOf("r")); // 6 - the first position of 'r'
console.log(airline.lastIndexOf("r")); // 10 - the last position of 'r'
consoele.log(airline.indexOf("portugal")); // -1 - string wasn't found
Removing Parts of String via .slice¶
const airline = "TAP Air Portugal";
console.log(airline.slice(4)); // Air Portugal - starts slicing at index position 4
// Substr length = end - beginning
console.log(airline.slice(4, 7)); // Air - starts at 4 and ends at position 7
Using .slice with .indexOf to get specific strings¶
const airline = "TAP Air Portugal";
console.log(airline.slice(0, airline.indexOf(" "))); // TAP - extracts the first name in the string, followed by the space afterwards
console.log(airline.slice(airline.lastIndexOf(" ") + 1)); // Portugal - starts slicing from the last ' ' position + 1
Get strings from last index first - Negative slicing¶
const airline = "TAP Air Portugal";
console.log(airline.slice(-2)); // al
console.log(airline.slice(1, -1)); // AP Air Portugal
Change string case¶
const airline = "TAP Air Portugal";
console.log(airline.toLowerCase()); // tap air portugal
console.log(airline.toUpperCase()); // TAP AIR PORTUGAL
Fix string capitalization¶
const passenger = "jOnas";
const passengerLower = passenger.toLowerCase();
const passengerCorrect = passengerLower[0].toUpperCase() + passenger.slice(1);
console.log(passengerCorrect); // 'Jonas'
Trimming strings¶
trim() function removes trailing white space at both start and end of a string.
String replacements¶
replace:
const priceGB = '$288,07'
const priceJP = priceGB.replace('$', 'Y').replace(',' '.');
console.log(priceJP) // 288.07$
replaceAll:
const announcement = "All passengers come to boarding door 23. Boarding door 23";
console.log(announcement.replaceAll("door", "gate")); // 'All passengers come to boarding gate 23. Boarding gate 23' - replaces all occurences of word "door" in the string with "gate"
- Replicating
replaceAllwith Regex:
console.log(announcement.replace(/door/g, "gate")); // 'All passengers come to boarding gate 23. Boarding gate 23'
String checks¶
Check if a word exists in a string¶
const plane = "Airbus A320";
console.log(plane.includes("Airbus")); // returns true
console.log(plane.includes("Boeing")); // returns false
console.log(plane.includes("Ai")); // returns true
Check if a string starts with sub-string¶
Check if a string ends with sub-string¶
const plane = "Airbus A320neo";
console.log(plane.endsWith("neo")); // true
if (plane.startsWith("Airbus") && plane.endsWith("neo")) {
console.log("Part of the NEW ARirbus family");
}
Split a string into an array¶
console.log("a+very+nice+string".split("+")); // ["a", "very", "nice", "string"]
const [firstName, lastName] = "Real Person".split(" "); // Real, Person
Combining an array into string¶
// using join
const newName = ["Mr.", firstName, lastName.toUpperCase()].join(" ");
console.log(newName);
Padding a string¶
In situations where the string needs to be a specified character length, we can use padding methods padStart and padEnd.
Convert a number to a string¶
String Repetition¶
Last update :
August 14, 2023
Created : August 23, 2022
Created : August 23, 2022