如何计算用户在文本表单中输入的特定符号的数量

Question

Sorry if it seems like a newbie question but I was wondering if there was a way to count the amount of specific symbols like a dot or slash in a URL style format that a person has entered.

var regex = /https?:\/\/(www\.)?[A-Za-z=:.]{1,12}\.[A-Za-z]{1,6}\b([-A-Za-z0-9%_\+=?&//#]){1,250}/
var validx = regex.test(document.getElementById("webname").value);

That's the regex and how Im calling the text input. So from that I was wondering if there was a way of counting the amount of symbols a user has entered.

I thought I could just call the function that contained a checker but it does not work

function dotcheck()
{
   var dots = detect.webname.value;
   if (dots.indexOf(".") > 0){}

the function where I thought you could see/count the amount of dots there

if (dotcheck = false){
            messages.innerHTML = 'Safe';

the if statement that I used to call the function.

Any help would be appreciated and if there is anything else you would need from me don't hesitate in asking.

Answer 1

The count of any character in a String is simply how many matches String.match(RegExp) returns.

Since you mentioned periods specifically, and those are special RegExp symbols, you can't just write /./g for your RegExp . You have to escape it with a \ , like this:

/\./g

The g flag appended to the end means get all matches, not just the first one.

 const string = 'https://stackoverflow.com/questions/62008355'; const slashes = /\//g; const count = string.match(slashes).length; console.log(count); // 4 slashes

 const string = 'https://stackoverflow.com/questions/62008355'; const periods = /\./g; const count = string.match(periods).length; console.log(count); // 1 period