nest-literal

Use string literals with functions and promises.

Usage

Synchronous usage

Substitutions used in nest string literals will be evaluated lazily, thus if they reference objects or functions, the value may be different at the time the template is stringified.

import nest from 'nest-literal'

function data() {
  return 'World'
}

const template = nest`Hello ${data}`

console.log(template.toString())

Asynchronous usage

If a substitution is a Promise, or a function that returns a promise, the promise can be resolved before the template is stringified if the template is used as a promise.

import nest from 'nest-literal'

async function data() {
  return 'World'
}

const template = nest`Hello ${data}`

console.log(await template)

Nested usage

You can nest templates. The resulting template is flattened.

import nest from 'nest-literal'

async function data() {
  return 'World'
}

const templateA = nest`Hello Data`
const templateB = nest`Foo ${templateA}, ${templateA} Bar`

console.log(await template)

Joining templates

If you have multiple templates, you can join them using join or .plus

import { nest, join } from 'nest-literal'

async function data() {
  return 'World'
}

const templateA = nest`Hello Data`
const templateB = nest`Foo ${templateA}, ${templateA} Bar`


// Using join 
const templateC = join(templateA, templateB)

// Using join with a delimiter
const templateC = join.with(',')(templateA, templateB)

// Using plus
const templateC = templateA.plus(templateB)

// Using reduce
const templateC = [templateA, templateB].reduce(join, null)

// Using reduce with a delimiter
const templateC = [templateA, templateB].reduce(join.with(','))


console.log(await template)

Using raw strings

If you want to manipulate your template and keep your values separate, you can use raw.

import { nest, raw } from 'nest-literal'

const tableName = 'MyTable'
const name = 'Leroy'

const sql = nest`select * from ${raw(tableName)} where name = ${name}`

Meta data

You can collect information about data injected into a template. .withMeta(...) allows to pass an object of metadata. Information is collected in the resulting template with a last-writer-wins policy. Scalar values are overwritten, Arrays are concatenated, Maps and Sets are merged.

import nest from 'nest-literal'

const hello = nest`Hello`.withMeta({
  last: 'hello',
  uses: ['Foo'],
  requires: new Set(['Admin', 'Guest'])
})
const world = nest`Hello`.withMeta({
  last: 'world',
  uses: ['Bar'],
  requires: new Set(['Admin', 'User'])
})
const combined = nest`${hello} ${world}`
console.log(combined.meta)

{
  last: 'world',
  uses: [ 'Foo', 'Bar' ],
  requires: Set(3) { 'Admin', 'Guest', 'User' }
}