Praktische Anwendungsfälle für Tagged Templates

Tags aus der Praxis

function tag(s, ...v) { return s[0] + v[0] + s[1] }
console.log(tag(["<", ">"], "b"))

Das Escaping-Problem

const danger = "<script>"
console.log("raw: " + danger)

Eine Escaping-Hilfsfunktion

function escapeHtml(str) {
  return String(str)
    .replace(/&/g, "&")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
}
console.log(escapeHtml("<b>"))

Sicherer HTML-Tag

function escapeHtml(str) {
  return String(str).replace(/</g, "&lt;").replace(/>/g, "&gt;")
}
function safe(strings, ...values) {
  let out = ""
  strings.forEach(function (s, i) {
    out += s + (values[i] !== undefined ? escapeHtml(values[i]) : "")
  })
  return out
}
console.log(safe(["<p>", "</p>"], "<script>"))

Warum statische Teile unverändert bleiben

function safe(strings, ...values) {
  let out = ""
  strings.forEach(function (s, i) {
    const safer = values[i] !== undefined ? String(values[i]).replace(/</g, "&lt;") : ""
    out += s + safer
  })
  return out
}
console.log(safe(["<b>", "</b>"], "<i>x</i>"))

Tag für formatierte Ausgabe

function money(strings, ...values) {
  let out = ""
  strings.forEach(function (s, i) {
    out += s + (values[i] !== undefined ? "$" + Number(values[i]).toFixed(2) : "")
  })
  return out
}
console.log(money(["Total: ", ""], 9.5))

Query-Strings erstellen

function url(strings, ...values) {
  let out = ""
  strings.forEach(function (s, i) {
    out += s + (values[i] !== undefined ? encodeURIComponent(values[i]) : "")
  })
  return out
}
console.log(url(["/search?q=", ""], "a b&c"))

Pluralbildung

function plural(strings, count) {
  const noun = count === 1 ? "item" : "items"
  return strings[0] + count + " " + noun
}
console.log(plural(["You have "], 1))
console.log(plural(["You have "], 3))

Einrückung entfernen

function dedent(strings) {
  return strings[0].split("\n").map(function (l) { return l.trim() }).join("\n")
}
console.log(dedent(["  a\n  b\n  c"]))

Tags kombinieren

function emph(strings, ...values) {
  let out = ""
  strings.forEach(function (s, i) {
    const v = values[i] !== undefined ? "**" + values[i] + "**" : ""
    out += s + v
  })
  return out
}
console.log(emph(["Note: ", "!"], "important"))

Wann Sie keine Tags verwenden sollten

const name = "Lee"
console.log("Welcome, " + name)

Schnelltest

Zusammenfassung

function safe(s, v) { return s[0] + String(v).replace(/</g, "&lt;") }
console.log(safe(["x="], "<a>"))