匹配javascript中的特定字符

Question

我有一個字符串，我想檢查它是否只包含允許的字符。

只允許字母a，b，c，d，e，k。我想到了這樣的事情：

var string1 = "abcdekabc" 
if (string1 contains only a,b,c,d,e,k) { 
    document.write("everything is fine"); 
} else { 
    document.write("there is one or more character that is not allowed"); 
} 

我該怎麼做？有一個正則表達式可以幫助我嗎？不幸的是，我沒有使用正則表達式的經驗。

Answer 1

是有一個正則表達式：

var pattern = new RegExp('[^abcdek]', 'i'); 
var string1 = "abcdekabc"; 
if(!pattern.test(string1)){ 
    document.write("everything is fine"); 
} else { 
    document.write("there is one or more character that is not allowed"); 
} 

這可以簡化爲：

var string1 = "abcdekabc"; 
if(!(/[^abcdek]/i).test(string1)){ 
    document.write("everything is fine"); 
} else { 
    document.write("there is one or more character that is not allowed"); 
} 

如果你願意，你可以以防萬一走另一條路（不檢查非法字符）：

var string1 = "abcdekabc"; 
if((/^[abcdek]+$/i).test(string1)){ 
    document.write("everything is fine"); 
} else { 
    document.write("there is one or more character that is not allowed"); 
}