JS - Semua tentang String Primitive

• Rentetan adalah primitif, masih ada kaedah yang boleh didapati pada objek.
• Setiap kali kita memanggil kaedah pada rentetan, JS menukarkan rentetan primitif kepada rentetan objek di belakang tabir dan kemudian pada objek itu yang kaedah dipanggil. Proses ini dipanggil tinju kerana String primitif diambil dan dimasukkan ke dalam objek String bertindak sebagai kotak iaitu ia menghantar hujah di dalam, kaedah "String() baharu" menukar rentetan primitif kepada objek rentetan.
• Apabila operasi selesai, objek ditukar kembali kepada String primitif daripada String objek di belakang tabir.
• Apa-apa sahaja yang dihantar ke 'String() baharu' menjadi objek yang boleh disahkan menggunakan operator jenis.

const car = 'Lamborghini Huracan EVO';

// Similarity of strings with arrays in JS
car[0];
car[car.length-1];
car.length;

// From begin
car.indexOf('o');
car.indexOf('Huracan');

// From end
car.lastIndexOf('E');

// index(begin, end) are used to extract part of string which are then passed to slice() as argument.
car.slice(car.indexOf('o'));
car.slice(8);
car.slice(8,15);  // Extracted string length will be (end-begin) as mentioned below

// String are primitives, hence immutable. Always use a data-structure to return a new string after the operation.

// Extract till a particular location inside an index.
car.slice(0, car.indexOf(' '));

// Extract the last word.
car.slice(car.lastIndexOf(' ')); // extracts along with space
car.slice(car.lastIndexOf(' ') + 1); // +1 added to exclude the space

// Extract from the end using negative values
car.slice(-7);
car.slice(1, -1);
car.slice(0, -1);

function knowYourSeatLocation(seat){
  const x = seat.slice(-1);
  if(x === 'W'){     console.log("Window Seat");  }
  if(x === 'M'){    console.log("Middle Seat");  }
  if(x === 'A'){    console.log("Aisle Seat");  }
}
knowYourSeatLocation('43W');
knowYourSeatLocation('12A');
knowYourSeatLocation('67M');

// Common Methods:
car.toLowerCase();
car.toUpperCase();
car.trim();
car.trimStart();
car.trimEnd();

// Methods returning boolean: Very good for conditional statements.
car.includes('Lambo');
car.startsWith('Lam');
car.endsWith('EVO');

// On taking user i/p convert it to lowercase before performing any operations on the text. It would eliminate a lot of error sources related to letter-case.

// Usage: Converting first letter to uppercase incase user enters name in mixed case to maintain consistency
// Usage: Email validation for characters esp whitespace, invalid characters etc.

// String replacement: (ToBeReplaced, ReplceWith)
// replace() : A case-sensitive method. Immutable Methods for functional Programming:
car.replace(' ','_');
car.replaceAll(' ','_');

// Using RegEx: Target text has to be enclosed between // with flag at the end. Desired text to be passed as second argument.
car.replace(/ini/g,'123456');

// .split(): split the text based on condition, return the elements in the form of an array
// .join(): opposite of .split()
car.split(''); // as characters
car.split(' '); // as words
car.split('i'); // based on a character

// Destrucutring makes it easier as compared to using .slice()
const name = 'Peter Parker';
const [fName, lName] = name.split(' ');
fName;
lName;

//  Adding saluttations to the name:
const title = ['Mr.', fName, lName.toUpperCase()].join(' ');
title;

// Usage: First letter of a Name capitalization
const capitalizeName = function(name){
  const names = name.split(' ');
  const namesUpper = [];

  for(const n of names){
    // Method 1 and Method 2 are listed below in two lines. Both work.
    // namesUpper.push(n[0].toUpperCase() + n.slice(1));
    namesUpper.push(n.replace(n[0],n[0].toUpperCase()));
  }
  console.log(namesUpper.join(' '));
};

capitalizeName('amar akbar anthony amarjeet');


// Padding a string i.e adding certain characters until a desired length is achieved.
// (DesiredLength, ToBePaddedWith)
const msg = 'Welcome to JS';
msg.padStart(20,'x');
msg.padEnd(20,'x');

// Convert a no into its string form by using: String()
// Another way is to add an '' to a number i.e When one operand of a + sign is string, all operands are converted into string form.

// Usage: Masking certain numbers of important documents
const maskedId = function(id){
  const str = id + '';
  const lastFour = str.slice(-4);
  return lastFour.padStart(str.length, '*');
}
maskedId(92837483297492);
maskedId('r438t7h4irgrgTAFE');


// repeat(NoOfTimeToBeRepeated) : Repeat the same text multiple times
const msgText = 'Raining.\n';
msgText.repeat(5 );

const TrainsWaiting = function(x){
  console.log(`There are ${x} trains waiting on the station ${'?'.repeat(x)} \n`);
}

TrainsWaiting(4);
TrainsWaiting(16);
TrainsWaiting(8);

// Extract string from a long text received from an API based on some separator found in text.
const data = 'Departure';

Atas ialah kandungan terperinci JS - Semua tentang String Primitive. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!