如何验证某个字符是否在 javascript 中的两个专用字符内？

Question

Let's say that the character we need to target is $ , and we need to verify if it lies between two ' & ' . The code will look something like this :

var str = " Verify '$' "
var str2 = " Let's see if ' The $ is inside ! ' "
var str3 = " I got $ "
console.log(verify(str)) //=> true
console.log(verify(str2)) //=> true
console.log(verify(str3)) //=> false

Javascript String.prototype.includes() , can be used to verify if $ exists in the string but I am not understanding how to verify if it is inside ' & ' ?

Answer 1

You could look for $ , wrapped by ' .

 const check = string => /'.*\\$.*'/.test(string); console.log([ " Verify '$' ", " Let's see if ' The $ is inside ! ' ", " I got $ "].map(check) );

Answer 2

This can be done using Regular Expressions :

 function verify(input) { const regex = RegExp(/'.*?\\$.*?'/); return regex.test(input); } var str = " Verify '$' " var str2 = " Let's see if ' The $ is inside ! ' " var str3 = " I got $ " console.log(verify(str)) //=> true console.log(verify(str2)) //=> true console.log(verify(str3)) //=> false

/'.*?\\$.*?'/ pattern description :

' matches the character ' literally (case sensitive)

.*? matches any character (except for line terminators)

*? Quantifier — Matches between zero and unlimited times , as few times as possible, expanding as needed (lazy)

\\$ matches the character $ literally (case sensitive)

.*? matches any character (except for line terminators)

*? Quantifier — Matches between zero and unlimited times , as few times as possible, expanding as needed (lazy)

' matches the character ' literally (case sensitive)

Answer 3

Its pretty hard to check if the $ is indeed between two ' and not between a pair of ' a ' and ' b 'b . So I would recommend iterating through the string and toggling a boolean whenever you see a quote. If you find a $ when the boolean is true check if there is a ' in the rest of the text;

 console.log(verify("'$'")) //=> true console.log(verify("' $ '")) //=> true console.log(verify("'a' $ '")) //=> false console.log(verify(" ' $ ")) //=> false function verify(text) { var openQuotes = false; for (var index = 0; index < text.length; index++) { if (text[index] === "'") openQuotes = !openQuotes; else if (text[index] === "$" && openQuotes && text.indexOf("'", index) !== -1) return true; } return false; }