template-literal-table

Tagged template literal mapping markdown style tables into objects.

Usage no npm install needed!

<script type="module">
  import templateLiteralTable from 'https://cdn.skypack.dev/template-literal-table';
</script>

README

Template literal - Table

Tagged template literal mapping markdown style tables into objects.

Inspired by the Jest test.each syntax.

Installation

$ npm install --save template-literal-table

Exports

The following functions are exported

name description
default The default export, this is table
table Table parser, skips divider rows (cell only containing two or more - characters) and rows consisting of empty cells
empty Table parser, skips divider rows, preserves rows consisting of empty cells
create Table parser creator, creates a new partser function with custom row filter functions

Usage

The template literal syntax allows for a lot of flexibility, as any type of value can be formatted without losing the actual value by providing the ${value} syntax. For fixed strings, you don't have to use the placeholder syntax if you don't care about its type (e.g. you cast it "manually" afterwards or its type is string anyway, which is what will be provided as).

const table = require('template-literal-table');

const records = table`
    foo  | bar   | baz
    -----|-------|-----
    ${1} | ${2}  | ${4}
    ${2} | ${4}  | ${8}
    4    | 8     | 16
`;

//  records = [
//    { foo: 1, bar: 2, baz: 4},
//    { foo: 2, bar: 4, baz: 8},
//    { foo: '4', bar: '8', baz: '16'},
//  ]

API

table (default)

The table function is the recommended use, as it parses table structures as most likely intended

import { table } from('template-literal-table');

const records = table`
    foo  | bar   | baz
    -----|-------|-----
         |       |
    one
         | two
         |       | three
    ${1} | ${2}  | ${4}
    ${2} | ${4}  | ${8}
    4    | 8     | 16
`;

//  records = [
//    { foo: 'one', bar: undefined, baz: undefined},
//    { foo: undefined, bar: 'two', baz: undefined},
//    { foo: undefined, bar: undefined, baz: 'three'},
//    { foo: 1, bar: 2, baz: 4},
//    { foo: 2, bar: 4, baz: 8},
//    { foo: '4', bar: '8', baz: '16'},
//  ]

empty

Like the table function, with the difference that empty lines will be preserved, do note that any newline in the table structure will become a new "row", regardless of the intention. This means that a trailing newline (as show below) will also result in a record with undefined values.

import { empty } from('template-literal-table');

const records = empty`
    foo  | bar   | baz
    -----|-------|-----
         |       |
    one
         | two
         |       | three
    ${1} | ${2}  | ${4}
    ${2} | ${4}  | ${8}
    4    | 8     | 16
`;

//  records = [
//    { foo: undefined, bar: undefined, baz: undefined},
//    { foo: 'one', bar: undefined, baz: undefined},
//    { foo: undefined, bar: 'two', baz: undefined},
//    { foo: undefined, bar: undefined, baz: 'three'},
//    { foo: 1, bar: 2, baz: 4},
//    { foo: 2, bar: 4, baz: 8},
//    { foo: '4', bar: '8', baz: '16'},
//    { foo: undefined, bar: undefined, baz: undefined},
//  ]

create

The table and empty function should cover most scenarios, though sometimes one needs different filters to be applied to the records passed in. For this purpose the create function exists, it allows any number of filters to be specified, which will be applied before the records are created from the values, meaning the filter functions will receive all values as argument.

The filter function signature is (...cells: unknown[]) => boolean

import { create } from 'template-literal-table';

// if the fourth column contains a value that is not a divider we want it to be present
const fourth = create((...values: unknown[]) => Boolean(values[3]) && !/^--+$/.test(String(values[3])) );
const records = fourth`
    one | two | three | four
    ----|-----|-------|------
    1   | 2   | 3     | 4
    1   | 2   | 3     |
    1   | 2   |       | 4
    1   |     | 3     | 4
        | 2   | 3     | 4
`;

//  records = [
//    { one: '1', two: '2', three: '3', four: '4' },
//    { one: '1', two: '2', three: undefined, four: '4' },
//    { one: '1', two: undefined, three: '3', four: '4' },
//    { one: undefined, two: '2', three: '3', four: '4' },
//  ]

Tips

Typed "columns"

In order to improve readability of a table, sometimes it's beneficial to not explicitly provide the true values within the table, but to cast it after it's been processed. Since the result of the table (and empty and the created ones) is an array of objects, this can be done using a simple map

const tableRaw = table`
    base | add  | result
    -----|------|--------
    ${1} | ${1} | ${2}
    ${1} | ${2} | ${3}
`;

const tableMapped = table`
    base | add  | result
    -----|------|--------
    1    | 1    | 2   
    1    | 2    | 3   
`.map(({ base, add, result }) => ({ base: Number(base), add: Number(add), result: Number(result) }));

Filters

Filters provided to the create function are applied after the "cell" values have been normalized and before the values are turned into the record objects.

This means that every cells' value has been trimmed of whitespace and the raw values are restored or merged if there's more than one. This process consists of the following steps:

  • remove trailing and leading space from the cell
  • restore the original value
  • if there's more than one value in a cell, merge it (this will always result in a string value)

In the table below some samples are shown:

 input         | typeof    | output             
---------------|-----------|--------------------
 1             | string    | (string) `'1'`     
 ${1}          | number    | (number) `1`       
---------------|-----------|--------------------
 true          | string    | (string) `'true'`  
 ${true}       | boolean   | (boolean) `true`   
 false         | string    | (string) `'false'` 
 ${false}      | boolean   | (boolean) `false`  
---------------|-----------|--------------------
 1 2           | string    | (string) `'1 2'`   
 ${1} 2        | string    | (string) `'1 2'`   
 1 ${2}        | string    | (string) `'1 2'`   
 ${1} ${2}     | string    | (string) `'1 2'`

License

MIT License Copyright (c) 2018-2021 Rogier Spieker

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.