string-strip-html^6.2.0

§ Quick Take

import { strict as assert } from "assert";
import stripHtml from "string-strip-html";

assert.equal(
  stripHtml(`Some text <b>and</b> text.`).result,
  `Some text and text.`
);

// prevents accidental string concatenation
assert.equal(
  stripHtml(`aaa<div>bbb</div>ccc`).result,
  `aaa bbb ccc`
);

// tag pairs with content, upon request
assert.equal(
  stripHtml(`a <pre><code>void a;</code></pre> b`, {
    stripTogetherWithTheirContents: [
      "script", // default
      "style", // default
      "xml", // default
      "pre", // <-- custom-added
    ],
  }).result,
  `a b`
);

// detects raw, legit brackets:
assert.equal(
  stripHtml(`a < b and c > d`).result,
  `a < b and c > d`
);

§ Examples

• program example: Extract HTML Head Contents
• program example: Leave Only HTML
• program example: Leave Only Opening td Tags
• program example: Leave Only td Tags
• program example: Remove All HTML from a String
• program example: Strip HTML from a Raw JSON String
• program example: Set the Title Case Using Title Package

§ Features

• Adds or removes the whitespace to make the output presentable.
• Removes tag pairs along with the content inside (handy for script).
• Works on broken, partial, incomplete, non-valid HTML.
• Works on HTML mixed with other languages (because it does not parse).
• Can be used to generate Email Text versions. Puts URL links.
• It can detect and skip false positives, for example, a < b and c > d.
• Enabled-by-default but optional Recursive HTML Decoding — nothing will escape!

§ API - Input

stripHtml(input, [opts])

In other words, it's a function which takes a string and an optional options.

If input arguments are supplied have any other types, an error will be thrown.

§ API - Output

The stripHtml() function will return a plain object, for example:

{
  log: {
    timeTakenInMilliseconds: 6
  },
  result: "abc click me def",
  ranges: [
    [3, 6, " "],
    [14, 18, " "],
  ],
  allTagLocations: [
    [3, 6],
    [14, 18],
  ],
  filteredTagLocations: [
    [3, 6],
    [14, 18],
  ],
}

Here is its API:

§ Optional Options Object

opts is a plain object. Here are all its keys:

The Optional Options Object is not validated; please take care of what values and of what type you pass.

Here is the Optional Options Object in one place (in case you ever want to copy it whole):

{
  ignoreTags: [],
  onlyStripTags: [],
  stripTogetherWithTheirContents: ["script", "style", "xml"],
  skipHtmlDecoding: false,
  trimOnlySpaces: false,
  dumpLinkHrefsNearby: {
    enabled: false,
    putOnNewLine: false,
    wrapHeads: "",
    wrapTails: ""
  },
  cb: null,
}

§ Using ranges from the output

The ranges from the output are compatible with range-ecosystem libraries like ranges-apply:

const stripHtml = require("string-strip-html");
const applyR = require("ranges-apply");

const input = `    <div>
  something
</div>
`;
const { result, ranges } = stripHtml(input);
console.log(ranges);
// => [[0, 12], [21, 32]]
console.log(result);
// => "something"

// apply ranges onto string:
const finalResultStr = applyR(input, ranges);
// you'll get same thing:
console.log(finalResultStr);
// => "something"

Behind the scenes, this program operates on ranges. The result string you see is rendered from ranges, at the time of returning.

§ opts.trimOnlySpaces

Hi  → Hi  instead of Hi  → Hi

In automated setups, a single string value can be split over multiple JSON paths. In those cases, joining spaces or non-breaking spaces are intended and often placed around the values. Normally, we would treat surrounding whitespace as a rogue, but not in these cases.

This setting allows us to distinguish between the two cases.

For example, imagine we "stitch" the sentence: Hi John! Welcome to our club. out of three pieces: Hi + John + ! + Welcome to our club.. In this case, spaces between the chunks would be added by your templating engine. Now, imagine, the text is of a quite large font-size, and there's a risk of words wrapping at wrong places. A client asks you to ensure that Hi and John are never split between the lines.

What do you do?

You remove the space between Hi and John from the template and move it to data-level. You hard-code the non-breaking space after Hi — Hi .

As you know, this library trims the input before returning it, and recursive HTML decoding is always on. On default settings, this library would remove your non-breaking space from Hi . That's where you need to set opts.trimOnlySpaces to true.

In this particular case, you can either turn off HTML decoding OR, even better, use this opts.trimOnlySpaces setting.

In either case, whitespace between the detected tags will still be aggressively trimmed - text <div>\n \t \r\n <br>\t \t \t</div> here → text here.

When this setting is on, only spaces will be trimmed from outside; an algorithm will stop at a first non-space character, in this case, non-breaking space:

"      &nbsp;     Hi! Please <div>shop now</div>!      &nbsp;      "

is turned into:

"      Hi! Please shop now!       "

Notice how space chunks between nbsp's and text are retained when opts.trimOnlySpaces is set to true. But the default is false; this feature is off by default.

§ opts.dumpLinkHrefsNearby

opts.dumpLinkHrefsNearby value is a plain object:

This feature is aimed at producing Text versions for promotional or transactional email campaigns.

If input string is has a linked text, URL will be put after it:

We watch both <a href="https://www.rt.com" target="_blank">RT</a> and
<a href="https://www.bbc.co.uk" target="_blank">BBC</a>.

it's turned into:

We watch both RT https://www.rt.com and BBC https://www.bbc.co.uk.

But equally, any link on any tag, even one without text, will be retained:

Codsen
<div>
  <a href="https://codsen.com" target="_blank"
    ><img
      src="logo.png"
      width="100"
      height="100"
      border="0"
      style="display:block;"
      alt="Codsen logo"
  /></a>
</div>

it's turned into:

Codsen https://codsen.com

Setting opts.dumpLinkHrefsNearby is off by default; you need to turn it on, passing options object with a key opts.dumpLinkHrefsNearby set to true.

§ opts.onlyStripTags

Sometimes you want to strip only certain HTML tag or tags. It would be impractical to ignore all other known HTML tags and leave those you want. Option opts.onlyStripTags allows inverting the setting: whatever tags you list will be the only tags removed.

opts.onlyStripTags is an array. When a program starts, it will filter out any empty strings and strings that can be String.trim()'ed to a zero-length string. It's necessary because a presence on just one string in opts.onlyStripTags will switch this application to delete-only-these mode and it would be bad if empty, falsy or whitespace string value would accidentally cause it.

This option can work in combination with opts.ignoreTags. Any tags listed in opts.ignoreTags will be removed from the tags, listed in opts.onlyStripTags. If there was one or more tag listed in opts.onlyStripTags, the delete-only-these mode will be on and will be respected, even if there will be no tags to remove because all were excluded in opts.onlyStripTags.

§ opts.stripTogetherWithTheirContents

This program not only strips HTML and returns a string. It also returns string index locations of removals. This way, you can use this program to extract ranges of indexes which would later be used to skip operations on a string.

For example, npm package title  capitalises the titles as per The Chicago Manual of Style. But if input source can contain HTML code, we need to skip processing the HTML tags.

The idea is, it sets opts.stripTogetherWithTheirContents to ["*"] — asterisk or wildcard meaning to "strip" all paired tags (including <code>/</code> in titles, for example). Then we take the locations of all tags and supplement it with locations of what's been whitelisted (using ranges-regex). Finally, we invert the ranges and supplement them with replacement value, third array element, coming from title. Here's the source code.

§ opts.cb

Sometimes you want more control over the program: maybe you want to strip only certain tags and write your custom conditions, maybe you want to do something extra on tags which are being ignored, for example, fix whitespace within them?

You can get this level of control using opts.cb. In options object, under key's cb value, put a function. Whenever this program wants to do something, it will call your function, Array.forEach(key => {})-style. Instead of key you get a plain object with the following keys:

const cb = ({
  tag,
  deleteFrom,
  deleteTo,
  insert,
  rangesArr,
  proposedReturn,
}) => {
  if (tag) {
    // do something depending on what's in the current tag
    console.log(JSON.stringify(tag, null, 4));
  }
  // default action which does nothing different from normal, non-callback operation
  rangesArr.push(deleteFrom, deleteTo, insert);
  // you might want to do something different, depending on "tag" contents.
};
const { result } = stripHtml("abc<hr>def", { cb });
console.log(result);

The tag key contains all the internal data for the particular tag which is being removed. Feel free to console.log(JSON.stringify(tag, null, 4)) it and tap its contents.

§ cb() example one

The point of this callback interface is to pass the action of pushing of ranges to a user, as opposed to a program. The program will suggest you what it would push to final ranges array, but it's up to you to perform the pushing.

Below, the program "does nothing", that is, you push what it proposes, "proposedReturn" array:

const cb = ({
  tag,
  deleteFrom,
  deleteTo,
  insert,
  rangesArr,
  proposedReturn,
}) => {
  rangesArr.push(deleteFrom, deleteTo, insert);
};
const res1 = stripHtml("abc<hr>def", { cb });
console.log(res1);
// => "abc def"

// you can request ranges instead:
const res2 = stripHtml("abc<hr>def", { cb });
console.log(res2);
// => [[3, 7, " "]]

§ cb() example two

In the example below, we are going to use one of the keys of the tag, the tag.slashPresent which tells is there a closing slash on this tag or not.

For example, considering input with some rogue whitspace, <div >abc</ div>, replace all div with tralala, minding the closing slash:

const stripHtml = require("string-strip-html");
// define a callback as a separate variable if you are going to use it multiple times:
const cb = ({
  tag,
  deleteFrom,
  deleteTo,
  // insert,
  rangesArr,
  // proposedReturn
}) => {
  rangesArr.push(
    deleteFrom,
    deleteTo,
    `<${tag.slashPresent ? "/" : ""}tralala>`
  );
};
const { result, ranges} = stripHtml("<div >abc</ div>", { cb });
console.log(result);
// => "<tralala>abc</tralala>"
console.log(ranges);
// => [
//      [0, 6, "<tralala>"],
//      [9, 16, "</tralala>"]
//    ]

§ Algorithm

Speaking scientifically, it works from lexer-level, it's a scanerless parser.

In simple language, this program does not use parsing and AST trees. It processes the input string as text. Whatever the algorithm doesn't understand — errors, broken code, non-HTML, etc. — it skips.

§ Licence

MIT 

Copyright © 2010–2020 Roy Revelt and other contributors