Gulp build does not install dependencies automatically?

I use gulp to build my javascript application. I have some dependencies declared in the package.json file, for example:

"dependencies": { "flux": "^2.0.1", "keymirror": "~0.1.0", "object-assign": "^1.0.0", "react": "^0.13.1", "dropzone": "^4.0.1", "lodash": "^3.6.0" },

When I run gulp build, it always prompt me some dependency cannot be found unless I manually run npm install lodash for example.

Is there a way to have gulp run npm install automatically?

thx a lot!