Javascript 检查第一个字符是数字、大写、小写还是特殊字符

Question

The goal is a program that checks if the first character they type is a number, uppercase letter, lowercase letter or a special character/other.

Number works absolutely fine, but my task has to compare the uppercase and lowercase and check if they are letters. If not, it should then return special character. I also have to make it without using functions.

I am struggling to get the special character to display as it is treated as either uppercase or lowercase. I have tried fiddling around with the equals signs and using regex but I am confusing myself. onlyLetters as you can see it not being used as I have tried making it == to input. Doing this led to everything (except numbers) being shown as a special character and thus reversing the problem. I have also tried seeing what works for others but they do not work on uppercase and lowercase letters also like I am.

Is there way to return an uppercase letter, lowercase letter or special character without the use of a function? Help to restore sanity is greatly appreciated

 let input = prompt('Enter a number or uppercase or lowercase letter') let onlyLetters = /^[a-zA-Z]/ const upperCase = input.toUpperCase() const lowerCase = input.toLowerCase() const numInput = Number(input) if (Number.isInteger(numInput) == true) { console.log(input + ' is a number') } else if (input === upperCase || lowerCase) { if (input === upperCase) { console.log(input + ' is an uppercase letter') } else if (input === lowerCase) { console.log(input + ' is a lowercase letter') } } else { console.log(input + ' is a special character') }

Answer 1

you have an error here

if (input === upperCase || lowerCase) {

should be

if (input === upperCase || input === lowerCase) {

But just use the regex you had but did not use

 let input = prompt('Enter a number or uppercase or lowercase letter') const numInput = Number(input) if (Number.isInteger(numInput)) { console.log(input + ' is a number') } else if (input.match(/[a-zA-Z]/)) { const upperCase = input.toUpperCase() const lowerCase = input.toLowerCase() if (input === upperCase) { console.log(input + ' is an uppercase letter') } else if (input === lowerCase) { console.log(input + ' is a lowercase letter') } } else { console.log(input + ' is a special character') }

Answer 2

let input = prompt('Enter a number or uppercase or lowercase letter')
const upperCase = input.toUpperCase()
const lowerCase = input.toLowerCase()
const numInput = Number(input)
charCode = input.charCodeAt(0)

if (Number.isInteger(numInput) == true) {
    console.log( input + ' is a number')
}

// 65 to 90 for uppercase
// 97 to 122 for lowercase

else if (charCode >= 65 && charCode <=90) {
    console.log(input + ' is an uppercase letter')
}

else if (charCode >= 97 && charCode <=122) {
    console.log(input + ' is a lowercase letter')
}

else {
    console.log(input + ' is a special character')
}

Answer 3

It looks like you are trying to determine the type of the input character. Here is one way to do it without using any functions:

let input = prompt('Enter a number or uppercase or lowercase letter')
let onlyLetters = /^[a-zA-Z]/

if (Number.isInteger(Number(input))) {
    console.log(input + ' is a number')
} else if (input >= 'A' && input <= 'Z') {
    console.log(input + ' is an uppercase letter')
} else if (input >= 'a' && input <= 'z') {
    console.log(input + ' is a lowercase letter')
} else {
    console.log(input + ' is a special character')
}

This solution checks if the input is a number, uppercase letter, or lowercase letter using simple comparisons. If none of those conditions are met, it is assumed that the input is a special character.