add event.js

Signed-off-by: arcticlion <david.malan@aol.com>
添加HTML特性使用event

Signed-off-by: arcticlion <david.malan@aol.com>
write a Usage of event.currentTarget&event.target in event.js

Signed-off-by: arcticlion <david.malan@aol.com>
write a Usage of event.currentTarget&event.target in event.js

Signed-off-by: arcticlion <david.malan@aol.com>
write a Usage of event.type in event.js

Signed-off-by: arcticlion <david.malan@aol.com>