Fast string template with tolerance to undefined

index.js

const _get = require('lodash/get');
const regEx = /\{\s*([a-zA-Z0-9\[\]\._]+)(\s*\|\s*['"]([^\}\s]+)['"])?\s*\}/g;


/*
 f({a: 1, b: { c: 2, d: 3}}, '({a}, {b.c}, {c.d})') will output (1, 2, 3)
*/

module.exports = (obj, str) => str.replace(regEx, (match, p1, p2, p3) => _get(obj, p1) || p3 || '');

index.test.js

var chai = require('chai');
var expect = chai.expect;
var _t = require('index.js');

var data = {
  address: {
    street: [
      "10E Hamilton Ave",
      "Ste 500"
    ],
    city: "Campbell",
    stateOrProvince: "CA",
    postalCode: "95008",
  }
}

// testUtils.enableSnapshots();

describe('utils/template', function() {
    it('Should return the right address', function() {
        const str = _t(data, '{address.street[0]} {address.street[1]}, {address.city}, {address.stateOrProvince} {address.postalCode}');
        chai.expect(str).to.matchSnapshot();
    });

    it('Should return the right address when a property is missing', function() {
        const str = _t(data, '{address.street[0]} {address.street[1]} {address.street[2]}, {address.city}, {address.stateOrProvince} {address.postalCode}');
        chai.expect(str).to.matchSnapshot();
    });

    it('Should be able to work with missing closed curly bracket', function() {
        const str = _t(data, '{address.street[0]} {address.street[1]}, {address.city}, {address.stateOrProvince} {address.postalCode');
        chai.expect(str).to.matchSnapshot();
    });

    it('Should be able to use default', function() {
        const str = _t(data, '{address.city} {address.noHere |  "alternate" }');
        chai.expect(str).to.matchSnapshot();
    });

    it('Default needs quotes', function() {
        const str = _t(data, '{address.city} {address.noHere | alternate }');
        chai.expect(str).to.matchSnapshot();
    });
});

index.test.js.snap

// Jest Snapshot v1, https://goo.gl/fbAQLP

exports[`utils/template Default needs quotes 1`] = `"Campbell {address.noHere | alternate }"`;

exports[`utils/template Should be able to use default 1`] = `"Campbell alternate"`;

exports[`utils/template Should be able to work with missing closed curly bracket 1`] = `"10E Hamilton Ave Ste 500, Campbell, CA {address.postalCode"`;

exports[`utils/template Should return the right address 1`] = `"10E Hamilton Ave Ste 500, Campbell, CA 95008"`;

exports[`utils/template Should return the right address when a property is missing 1`] = `"10E Hamilton Ave Ste 500 , Campbell, CA 95008"`;