diff_kit

Deno lib that compares 2 strings and generates result like assertEquals(), also in HTML.

Example

import {diff, DiffText, DiffTerm, DiffHtml} from 'https://deno.land/x/diff_kit@v0.0.5/mod.ts';

const left =
`abc
def
`;
const right =
`abc
de*f
`;

console.log('--- Default (terminal colors) ---');
let result = diff(left, right);
console.log(result);

console.log('--- Plain text ---');
result = diff(left, right, new DiffText({indentWidth: 2}));
console.log(result);

console.log('--- Terminal colors ---');
result = diff(left, right, new DiffTerm({indentWidth: 2}));
console.log(result);

console.log('--- HTML ---');
result = diff(left, right, new DiffHtml({indentWidth: 2}));
console.log(result);

diff()

The main function that this module is exporting is called diff().

interface DiffSubj
{	readonly length: number;
    charCodeAt(i: number): number;
    slice(from: number, to: number): string;
}

function diff(left: DiffSubj, right: DiffSubj, diffHandler: DiffHandler=new DiffTerm({indentWidth: 4}))

The DiffSubj interface is string-compatible, and the most usual use case is to pass strings to the diff() function.

Extending this library

This library contains 3 classes that provide visualization of the diff result: DiffText, DiffTerm and DiffHtml. They are subclasses of DiffHandler.

If you want to generate the result in a different way you can create your own subclass of DiffHandler.

The DiffHandler class has exactly this implementation:

class DiffHandler
{	protected result = '';

    addEqual(part: string)
    {	this.result += part;
    }

    addDiff(partLeft: string, partRight: string)
    {	if (partRight)
        {	this.result += '[-]';
            this.result += partRight;
        }
        if (partLeft)
        {	this.result += '[+]';
            this.result += partLeft;
        }
        this.result += '[=]';
    }

    toString()
    {	return this.result;
    }
}

It can be used as parameter to diff() without subclassing, and so the very basic plain text diff will be generated (deleted parts will be marked with [-]...[=], inserted parts with [+]...[=], and changed parts with [-]...[+]...[=]).

When passing an instance of DiffHandler (or it’s subclass) to the 3rd parameter of diff(), the following methods of the handler get called:

• addEqual(part: string) add a text part that is the same for both the left-hand and the right-hand side of the diff.
• addDiff(partLeft: string, partRight: string) add part that is different. One of partLeft or partRight can be empty (but not both).
• toString() - at last, the object is converted to string to get the result.

The same method is not called twice in sequence. That is, for example, after addEqual() will be called either addDiff() or toString().

So you can create an extension to this library, and use it in your project, or to publish it to deno.land/x. It’s recommended to prefix the library name with diff_kit_ex_.