Array of objects on a json - http put [duplicate]

Question

I have the following Json structure on my project:

"disputas": [
    {
      id: "",
      tipo_negociacao: "",
      historico:[{
         fl_usuario: "",
         created_at: "",
         updated_at: "",
         created_by: null,
         updated_by: null,
         texto: "",
      }]
    }
]

I want to add a new index of historico when I click on a button but don't know how to do it, I want it to look like this:

 "disputas": [
        {
          id: "",
          tipo_negociacao: "",
          historico:[{
             fl_usuario: "",
             created_at: "",
             updated_at: "",
             created_by: null,
             updated_by: null,
             texto: "",
          },
           {
             fl_usuario: "",
             created_at: "",
             updated_at: "",
             created_by: null,
             updated_by: null,
             texto: "",
          }

       ]
    }
]

So far, I've done something like this (function that the button calls):

     recusaProposta() {
        this.disputa.historico[this.i].texto = "something";   
        this.i++;
}

now, since i starts on 0 this works on the first time I click on the button, but if I click on it again I'll get this error:

Cannot set property 'texto' of undefined

Can someone help me? thanks

Answer 1

Just push a new item to the historico array:

this.disputa.historico.push({
fl_usuario: "",
             created_at: "",
             updated_at: "",
             created_by: null,
             updated_by: null,
             texto: ""
});

Answer 2

Just append an array:

this.disputa.historico.push({/* your object here*/});

Answer 3

You run into the error

Cannot set property 'texto' of undefined

when you try to access a property on a undefined or null object.

You will first have to create a empty object in its place, if not already existing. The way your code is, it is expecting the object to be present in the index you are trying to access.

var existingObj = this.disputa.historico[this.i];

// if the value is falsy, then go ahead and create
// an empty object at that index
if(!existingObj) {
   this.disputa.historico[this.i] = {};
}

existingObj.texto = "something";

Answer 4

Try this

disputas.historico.push({/* obj*/});