An essential point to remember a training course is to take notes and discuss the subject with others. That's why every day I will post on dev.to the concepts and notes that I learned the day before.
If you want to miss nothing click follow and you are welcome to comments and discuss with me.
Without further ado here is a summary of my notes for today.
String
const name = 'Mike Taylor'
// direct character access
console.log(name[0]) // M
// Get position (zero base)
console.log(name.indexOf('T')) // 5
// Modify one element
name[0] = 'P' // Pike Taylor
// Extract (slice) part or a string (start, stop before)
console.log(name.slice(5)) // Taylor
console.log(name.slice(5, 8)) // Tay
console.log(name.slice(-2)) // or
// Convert to lower or upper case
console.log(name.toLowerCase()) // mike taylor
console.log(name.toUpperCase()) // MIKE TAYLOR
// Remove white space
const title = ' This is a title with space '
console.log(title.trim()) // 'This is a title with space'
// Chaining string method
console.log(title.toLowerCase().trim()) // 'this is a title with space'
// replace
const name = 'Mike Taylor'
console.log(name.replace('Mike', 'Paul') // Paul Taylor
// includes?
const name = 'Mike Taylor'
console.log(name.includes('Mike')) // true
// Split
const colors = 'Red, Green, Blue')
console.log(colors.split(',')) // ['Red', 'Green', 'Blue']
// Join
const colors = ['Red', 'Green', 'Blue']
const colors_string = colors.join('-') // Red-Green-Blue
Short-circuit || operator
// if first value truthy then return first value
// if first value falsy then return second value
console.log('Hello' || 'Hi') // 'Hello'
console.log('' || 'Bye') // 'Bye'
console.log('' || 0 || 100) // 100
// Assignment example
const maxUser = config.maxUser || 10
Nullish Coalescing operator
// Only assign if null or undefined
const maxUser = config.maxUser ?? 10
Optional chaining
if (customer.creditLimit) {
if (customer.creditLimit.dateExpire) {
console.log(customer.creditLimit.dateExpire)
}
}
console.log(customer.creditLimit.dateExpire) // error
// optional chaining: assign only if not undefined or null
console.log(customer.creditLimit?.dateExpire) // undefined
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