Strict tag

An es2015 template tag function that validates template substitutions to guard against null and undefined values. Because sometimes, you really don't want "undefined" or "null" in your strings.

For example, urls are usually somewhere where you want to be strict:

const fooId;
fetch(`/foos/${fooId}`).then(...)

In this case, you're going to be trying to figure out why you're getting a 404 on /foo/undefined. Stop the request from even happening with a more specific error using strict:

const strict = require('strict-tag');
const fooId;
fetch(strict`/foos/${fooId}`).then(...)

This would throw an error during the template evaluation:

/Users/johnvh/dev/strict-tag/index.js:17
      throw new StrictTemplateError(`Template substitution at index ${i} is invalid`);
      ^

StrictTemplateError: Template substitution at index 0 is invalid
    at StrictTemplateError (/Users/johnvh/dev/strict-tag/index.js:3:5)
    at /Users/johnvh/dev/strict-tag/index.js:17:13

Usage

Install: npm install strict-tag

Use:

const strict = require('strict-tag');
console.log(strict`pid: ${process.pid}`);

strict

Default export. A template tag function that throws a StrictTemplateError if any substitutions are null or undefined.

strict.with(isInvalidFn)

A factory to create a template tag function that validates arguments using the isInvalidFn predicate function. isInvalidFn is invoked with each subtitution:

const _ = require('lodash');
const strict = require('strict');
const strictEmpty = strict.with(_.isEmpty);
const a = '';
console.log(strictEmpty`hello ${a}`); // throws

strict.StrictTemplateError

An error for invalid template substitutions.