If语句比较lastName是否以字母A-L开头

Question

我试着运行这个代码，但它不工作，能有人帮忙吗?

var lastName = document.queryselector('lastName');
var message = document.queryselector('message');
function checkFirstLetterOfLastName() {
 if (/^[A-L]/.test(lastName)) {
 message.textContent = 'Go stand in first line';
 } else {
 message.textContent = 'Go stand in first line';
 }
}
checkFirstLetterOfLastName();

Answer 1

下面是一个使用正则表达式的工作示例:

function checkFirstLetterOfLastName(lastName) {
  if (/^[A-L]/.test(lastName)) {
    console.log(lastName, 'starts with A-L');
  } else {
    console.log(lastName, 'does not start with A-L');
  }
}
checkFirstLetterOfLastName('Carlson');
checkFirstLetterOfLastName('Mathews');

Answer 2

 function checkFirstLetterOfLastName(lastname) {
  if((/^[A-L].+/i).test(lastname)) {
    console.log('starts with A-L');
  }
  else
  {
     console.log('does not starts with A-L');
  }
}
checkFirstLetterOfLastName("hello")

Answer 3

foo('Avery');
foo('David');
foo('Laura');
foo('Michael');
foo('Zachary');
function foo(x) {
  if(x.match(/^[A-L]/i)) {
    console.log('Go stand in first line.')
  }
  else console.log('Go stand in second line.');
}

这个对你有用吗?

Answer 4

我将使用RegEx并使用expression.test方法，如下所示:

// a string that starts with a letter between A and L
var str = 'Hello!'
// a string that does not start with a letter between A and L
var notPass = 'SHould not pass'
// Note: this only checks for capital letters
var expr = /[A-L]/
console.log(expr.test(str[0]))
console.log(expr.test(notPass[0]))