Converts a multiline string into a <p>...</p> separated string for HTML use.

paragraphs.js

function toParagraphs(string){
  return string.split(/[\r?\n]+/g)
    .map(p => p.trim())
    .filter(p => p.length > 0)    
    .map(p => `<p>${p}</p>`)
    .join("");
}

// Tests

let testData = [
  [` 456   `, "<p>456</p>"],
  [`a`, "<p>a</p>"],
  [`a\nb	`, "<p>a</p><p>b</p>"],
  [`    `, ""],
  [`\n\n`, ""],
  [` \n \t  \n `, ""],
  [`\na`, "<p>a</p>"],
  [`a\n`, "<p>a</p>"],
  [`a\n\n`, "<p>a</p>"],
  [`\na\n`, "<p>a</p>"],
  [`\na\n\n`, "<p>a</p>"],
  [`\na\t\n\t\nb\t`, "<p>a</p><p>b</p>"]
];

let testDataMultiline = [
	[`
    
    1
    2
    
    3
    `, "<p>1</p><p>2</p><p>3</p>"],

    [`a
    b	`, "<p>a</p><p>b</p>"],
    
    [`
 AAA

     11

22222
3
44

5
6

777
`, "<p>AAA</p><p>11</p><p>22222</p><p>3</p><p>44</p><p>5</p><p>6</p><p>777</p>"]


];

testDataMultiline.concat(testData).map(d => {
	console.assert(toParagraphs(d[0]) === d[1]);
});