npm install gulp-change

var gulp = require('gulp');
var change = require('change');

function performChange(content) {
    return content.replace(/foo/g, 'FOO');
}

gulp.task('change', function() {
    return gulp.src('src/*.html')
        .pipe(change(performChange))
        .pipe(gulp.dest('build/'))
});

var gulp = require('gulp');
var change = require('change');

function performChange(content, done) {
    content.replace(/foo/g, 'FOO');
    done(null, content);
}

gulp.task('change', function() {
    return gulp.src('src/*.html')
        .pipe(change(performChange))
        .pipe(gulp.dest('build/'))
});