如何使用正则表达式确定标头级别（JavaScript）

Question

I am using Node.js to read a markdown file for my workplaces orders we take from customers. I am seperating the files into arrays of lines, and performing a check on each line to see what is it (h1, h3, task, etc) but am having lots of trouble getting my RegExps to work correctly. Here is the code I have so far:

var filesystem = require('fs');
let content;
let missingItems = [];

filesystem.readFile('orders.md', 'utf8', (err, res) => {
    let content = res;
    let lines = content.split('\n');
    lines.forEach(line => {
        if(line.match(/#{1}/)){
            console.log('Store Name: ', line);
        };
    });
});

This code, however returns all h1 AND h3 lines. I saw using RegExp 101 online that the problem is that my RegExp is being matched 3 times for the h3 lines and one time for the h1 lines.

How can I write a regular expression that will not return true for both h1 and h3 lines? I don't understand why this matches 3 times when I'm explicitly saying match {1} ( ONCE )

This is the testing area I've been testing my expressions with and some example text of what I am trying to test against: RegExp101

Answer 1

You're asking if the line contains (at least) one # with that regex, which both lines do. you could use a negative lookahead:

^#(?!#)

^ means 'start of line', then the literal pound symbol, then the negative lookahead that takes the form of (?!pattern) , so we're looking ahead to NOT see another pound symbol.

Much simpler would be to test for the inital # and a following space \\s :

^#\\s