@putout/printer

Printer

Prints Babel AST to readable JavaScript.

• ☝️ Similar to Recast, but simpler and easier in maintenance, since it supports only Babel.
• ☝️ As opinionated as Prettier, but has more user-friendly output and works directly with AST.
• ☝️ Like ESLint but without any configuration and plugins 🤷‍, also works directly with Babel AST only.

Install

npm i @putout/printer

API

const {print} = require('@putout/printer');
const {parse} = require('@babel/parser');
const ast = parse('const a = (b, c) => {const d = 5; return a;}');

print(ast);

// returns
`
const a = (b, c) => {
    const d = 5;
    return a;
};
`;

Overrides

When you need to extend syntax of @putout/printer just pass a function which receives:

• path, Babel Path
• print, a function to output result of printing into token array;

When path contains to dashes __ and name, it is the same as: print(path.get('right')), and this is actually traverse(path.get('right')) shortened to simplify read and process.

Here is how you can override AssignmentPattern:

const ast = parse('const {a = 5} = b');

print(ast, {
    format: {
        indent: '    ',
    },
    visitors: {
        AssignmentPattern(path, {print}) {
            print(' /* [hello world] */= ');
            print('__right');
        },
    },
});

// returns
'const {a /* [hello world] */= 5} = b;\n';

Maybe

When you need some condition use maybe. For example, to add newline only when parent node is CallExpression you can use maybe.print.newline(condition):

print(ast, {
    visitors: {
        AssignmentPattern(path, {print, maybe}) {
            maybe.print.newline(path.parentPath.isCallExpression());
            print(' /* [hello world] */= ');
            print('__right');
        },
    },
});

License

MIT