Check if Value of HTML Input Text Field is Integer in Go

Check if the value of HTML input text field is integer in Go. Compiled to JavaScript using GopherJS.

Demo

Note that above demo is written in JavaScript, and is not 100% the same as the following demo written in Go. You have to compile the Go code to JavaScript using GopherJS. The JavaScript demo is not very correct, because if you input 2.1, it will tell you it's integer 2 because of JavaScript parseInt() method treats 2.1 as 2. The Go demo is correct, and it will tell you 2.1 is invalid.

The following are source code in Go and HTML.

HTML

<input type="text" name="n">
<button type="button" id="check">Check Integer</button><br><br>
<div id="result"></div>

Go (appdom.go): This file use github.com/siongui/godom. Please go get it before compiling this file using GopherJS.

We use strconv.Atoi in Go standard library to convert the string to integer for us. If the input is not integer, error will be returned.

package main

import (
      . "github.com/siongui/godom"
      "strconv"
)

func main() {
      elmn := Document.QuerySelector("input[name='n']")
      btn := Document.QuerySelector("#check")
      info := Document.QuerySelector("#result")

      btn.AddEventListener("click", func(e Event) {
              _, err := strconv.Atoi(elmn.Value())
              if err != nil {
                      info.SetInnerHTML(err.Error())
                      return
              }
              info.SetInnerHTML("input is integer")
      })
}

The link of full source code is available on my GitHub repo.

Tested on:

• Chromium 65.0.3325.181 on Ubuntu 17.10 (64-bit)
• Go 1.10.1
• GopherJS 1.10-3

References: