javascript - 即使满足了要求， else if 语句也不会运行？

Question

function illegal_chr(input) {
//checks 'entry_box' for illegal characters
document.getElementById("binary_p").innerHTML = "Convert binary to text or text to binary."
var entry_value = document.getElementById("entry_box").value;
var entry_length = entry_value.length
var CHARACTERS_ARRAY = []
var illegal_message_bin = "Please ensure you have only used binary."
var ILLEGAL_BIN = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "[", "]", "#", "'", ";", ",", ".", "`", "¬", "?", ">", "<", "~", "@", ":", "}", "{", "|", "/", "!", "£", "$", "%", "^", "&", "*", "(", ")", "_", "-", "+", "=", "2", "3", "4", "5", "6", "7", "8", "9"]

//adds each character to 'CHARACTERS_ARRAY'
for (var c = 0; c < entry_length; c += 1) {
    character = entry_value[c];

    CHARACTERS_ARRAY.push(character)
}

//loops through 'CHARACTERS_ARRAY' checking for any illegal characters
for (var ch = 0; ch < CHARACTERS_ARRAY.length; ch += 1) {
    characters = CHARACTERS_ARRAY[ch];

    for (var ill = 0; ill < ILLEGAL_BIN.length; ill += 1) {
        letters = ILLEGAL_BIN[ill]

        if (characters == letters) {
            document.getElementById("binary_p").innerHTML = illegal_message_bin;
        }

        else if (characters != letters && ch == entry_length) {
            alert("test")
        }
    }
}
}

该函数检查用户是否使用了任何“非法字符”，这可以工作，但是当它不包含“非法”字符时，什么也不会发生？

Answer 1

请注意，您可以使用正则表达式，如 @duffymo 所说:

function isHex(str) {
    return str.match(/^[a-f0-9]{6}$/i) !== null;
}

这会检查二进制数(至少一个 0 或 1):

function isBin(str) {
    return str.match(/^[0,1].*$/) !== null;
}