Golang : Inject/embed Javascript before sending out to browser example
Problem:
You want to grab some Javascript code from other sources such as an external server or you simply want to separate the Javascript code from your Golang code instead of lumping them together.
Once you grabbed the Javascript code, you want to inject/embed in your HTML code before sending it out to the ResponseWriter/client/browser.
How to do that?
Solution:
Use http.Get()
to get JavaScript from another server/URL or use ioutil.ReadFile()
to get from file. Next, combine the Javascript code into HTML before writing to ResponseWriter.
Below is an example that you can test out on localhost.
Here you go!
package main
import (
"fmt"
"io/ioutil"
"net/http"
"os"
)
func SayHelloWorld(w http.ResponseWriter, r *http.Request) {
html := `<!DOCTYPE HTML><html><body>Hello World
`
response, err := http.Get("http://localhost:8080/js") // or some external sources
if err != nil {
fmt.Println(err)
os.Exit(1)
}
defer response.Body.Close()
javascript, err := ioutil.ReadAll(response.Body) //<--- here!
if err != nil {
fmt.Println(err)
os.Exit(1)
}
html = html + string(javascript)
html = html + `
</body></html>`
w.Write([]byte(html))
}
func InjectJavaScript(w http.ResponseWriter, r *http.Request) {
js := `<script type="text/javascript" charset="utf-8">
alert("View page source to see injected/embedded Javascript code!");
</script>`
w.Write([]byte(js))
}
func main() {
mux := http.NewServeMux()
mux.HandleFunc("/", SayHelloWorld)
mux.HandleFunc("/js", InjectJavaScript)
http.ListenAndServe(":8080", mux)
}
Hope this helps!
References:
https://www.socketloop.com/tutorials/golang-convert-http-response-body-to-string
https://www.socketloop.com/tutorials/golang-read-file-with-ioutil
https://www.socketloop.com/tutorials/golang-http-server-example
See also : Golang : Daemonizing a simple web server process example
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+15.1k Golang : Execute terminal command to remote machine example
+3.9k Unix/Linux : How to pipe/save output of a command to file?
+10.8k Golang : Perform sanity checks on filename example
+3.9k Nginx and PageSpeed build from source CentOS example
+14.1k Golang : rune literal not terminated error
+10.5k Golang : Secure file deletion with wipe example
+27.6k Golang : Saving(serializing) and reading file with GOB
+12.2k Golang : Convert(cast) int to int64
+6.6k SSL : How to check if current certificate is sha1 or sha2 from command line
+5.1k AWS S3 : Prevent Hotlinking policy
+17.8k Golang : When to use public and private identifier(variable) and how to make the identifier public or private?
+3.8k JavaScript : Rounding number to decimal formats to display currency