需要检查@符号前面是否有字符串

function checkStringBeforeAtSymbol(str) {
  var index = str.indexOf('@');
  if (index !== -1 && index !== 0) {
    return true;
  } else {
    return false;
  }
}

var input = 'example@domain.com';
var result = checkStringBeforeAtSymbol(input);
console.log(result); // 输出 true

import re

def check_string_before_at_symbol(string):
    pattern = re.compile('.*@')
    match = pattern.match(string)
    if match:
        return True
    else:
        return False

input = 'example@domain.com'
result = check_string_before_at_symbol(input)
print(result) # 输出 True