Edit in JSFiddle

var cont = document.getElementById('rs')
var ln = `\n`
var line = `\n${'#'.repeat(64)}\n`
let msg = "Hello World!"

cont.textContent = msg
cont.textContent += line
cont.textContent += ln + `msg.startsWith("Hello"): ` + msg.startsWith("Hello")
cont.textContent += ln + `msg.endsWith("!"): ` + msg.endsWith("!")
cont.textContent += ln + `msg.includes("o"): ` + msg.includes("o")

cont.textContent += line
cont.textContent += ln + `msg.startsWith("o"): ` + msg.startsWith("o")
cont.textContent += ln + `msg.endsWith("world!"): ` + msg.endsWith("world!")
cont.textContent += ln + `msg.includes("x"): ` + msg.includes("x")


cont.textContent += line
cont.textContent += ln + `msg.startsWith("o", 4): ` + msg.startsWith("o", 4)
cont.textContent += ln + `msg.endsWith("o", 8): ` + msg.endsWith("world!")
cont.textContent += ln + `msg.includes("x"): ` + msg.includes("x")

<pre id="rs"></pre>