READ (SELECT/GET)

Somewhere on a page you must trigger the call to get the data. One way is to add a path to a button

<button onclick="api3get('tsk/all')">Call Javascript</button>

The AJAX Request accepts dynamic call (+path) and writes back to the HTML page target (id="data")

function api3get(path) {
var url = "https://api3.go4webdev.org/"+path;
var xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.setRequestHeader("Accept", "application/json");
xhr.onload = function() {
if (xhr.readyState === 4) {
document.getElementById("data").innerHTML = this.responseText
}
};
xhr.send();
}

Instead of storing each Query in the API, the query is stored in a database (almost similar to the Postgresql view function) fetched for each request. This means easier to maintain and more generic API (fewer endpoints)

The query is fetced with an id "tsk_all" from the REST call https://api3.go4webdev.org/tsk/all

func Getquery(path string) string {
// get query from lookup db
var query string
err := db.QueryRow("SELECT sql_query FROM sqls WHERE sql_id=$1", path).Scan(&query)
if err != nil {
path = ""
}
fmt.Println(query)
return query
}

The lookup Query look like this with a parameter that is filled with JSON from the form in the next step

SELECT * FROM tsk;

The READ endpoint in the Go API contains both executing the query as well as return data back to the client.

package main

import (
"encoding/json"
"fmt"
"net/http"
"net/url"
)

func Get(w http.ResponseWriter, r *http.Request) {
scope, action, val := getpath(r)
var data interface{}
val, _ = url.QueryUnescape(val)

switch action {
case "id":
query := Getquery(scope + "_" + action)
data = getid(query, val)
fmt.Println(query)
case "all":
query := Getquery(scope + "_" + action)
data = getall(query)
}

json.NewEncoder(w).Encode(data) //write back to client
}

// return a single row
func getid(query string, val string) interface{} {
if len(query) > 0 {
row := make(map[string]interface{})
db.QueryRowx(query, val).MapScan(row)
return (row)
}
return nil
}

// query to return a list
func getall(query string) interface{} {
fmt.Println(query)
if len(query) > 0 {
var list []map[string]interface{}
rows, err := db.Queryx(query)

if err != nil {
log("no records")
}

defer rows.Close()

for rows.Next() {
row := make(map[string]interface{})
err = rows.MapScan(row)
if err != nil {
  log(err.Error())
}
list = append(list, row)
}

rows.Close()
if len(list) == 0 {
return ("norec")
}
return list
}
return nil
}

The data appears in the tag id="data"

<div id="data">The result</div>