Read JSON file by Javascript

Question

I need to read a JSON file by Javascript and assign each item of it to a single variable, as I did in this algorithm:

function leitura(){
   var arquivo = **Ler arquivo**('json/teste.json');
   var conteudo;
   **Laço de repetição**{
       conteudo += arquivo.nome + ', ';
   }
   alert(conteudo);
}

Answer 1

You will need to request your json using the object Xmlhttprequest thus below:

var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
       var myObj = JSON.parse(this.responseText);
       document.getElementById("demo").innerHTML = myObj.name;
    }
};
xmlhttp.open("GET", "json_demo.txt", true);
xmlhttp.send();

Then the object analyzes the return of the request made by the object Xmlhttprequest and checks that the httpd status is valid (200) and transforms the return of the file (string) to a json using the javascript function JSON.parse, then you can read the json entries one by one to your variable as you did above in your example.

Deepen your knowledge here : read Json with javascript

To run when the page loads you have to use an event, like this:

window.onload = function(){
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.onreadystatechange = function() {
       if (this.readyState == 4 && this.status == 200) {
           var myObj = JSON.parse(this.responseText);
           document.getElementById("demo").innerHTML = myObj.name;
       }
   };
   xmlhttp.open("GET", "json_demo.txt", true);
   xmlhttp.send();
}

window.onload serves to execute the code after the page load is complete.