gulpfile.js

const gulp = require('gulp');
const ts = require('gulp-typescript');
const jasmine = require('gulp-jasmine');

gulp.task('build', function() {
    const merge = require('merge2');
    const tsProject = ts.createProject('tsconfig.json');

    var tsResult = tsProject.src()
        .pipe(tsProject());

    return merge([
        tsResult.dts.pipe(gulp.dest('./definitions')),
        tsResult.js.pipe(gulp.dest(tsProject.config.compilerOptions.outDir))
    ]);
});