I have been trying to access array member from an Array (data_array).My variable data_array is part of json something similar to code below. The code below is not the actual code. The actual code is coming in play when i am trying to create a React component. I can paste the complete React component but it would contain some unnecessary information. So i thought i would add some mock example. Apologies if it misled people. Currently i was hoping to get some hints on what could possibly go wrong in such scenario? :
data: {
"name": "Arjun",
"records" : [
{
"value": 3
},
{
"value": 6
},
{
"value":7
}
]
}
var data_array = data.records
console.log(data_array) -> Array[3]
console.log(data_array[0]) -> It displays Uncaught TypeError: Cannot read property '0' of undefined
console.log(typeof data_array) -> Object.
What's confusing to me is my first output as it says its an Array.I am fairly new to javascript. So maybe i am missing something. Any help would be appreciated.
Edit: This would still be missing a nested React Component but it would be of no use in this case. I am calling the nested component Foo for now
var React = require('react'),
Router = require('react-router'),
mui = require('material-ui'),
Foo = require('./foo.jsx');
var TempReact = React.createClass({
mixins: [Router.Navigation],
getInitialState: function() {
return {
data: {}
};
},
componentDidMount: function() {
// Do a web request here to actually get the data from the backend API
// this.setState({
// });
// For now, load our fake data
this._loadFakeData();
},
render: function() {
//console.log(this.state.data)
for(var record in this.state.data.records) {
console.log(record.Value);
}
//console.log(this.state.data["records"][0]["Value"])
return (
<div>
<p>^ That will still say , since the header up there is decided by temp-page.jsx, which is
based on the route</p>
<br/>
<p>We've loaded the fake data into our component's state, and here's proof:</p>
{this.state.data.name}
<br/>
<br/>
<Foo name={["temp1",this.state.data.records,"green"]}/>
</div>
);
},
_loadFakeData: function() {
this.setState({
data: {
"name": "Arjun",
"records" : [
{
"Value": 6
},
{
"Value": 7
},
{
"Value": 8
}
]
}
});
}
});
module.exports = TempReact;
Arrays are typeof Object. They're just an object with some fancy stuff going on.
The following example works:
var data = {
"name": "Arjun",
"records" : [
{
"value": 3
},
{
"value": 6
},
{
"value":7
}
]
}
var data_array = data.records
console.log(data_array[0]) // Object {value: 3}
This error happens when you do something like this:
var data = {};
var data_array = data.array; // data.array is undefined and subsequently data_array.
console.log(data_array[0]); // Throws: Uncaught TypeError: Cannot read property '0' of undefined
You're not far off lets say you store this object in a variable called jsonData just for an example :
var jsonData = {
data: {
"name": "Arjun",
"records" : [
{
"value": 3
},
{
"value": 6
},
{
"value":7
}
]
}
}
You'll need to access the variable > property > nested property , then specify the index like so :
var data_array = jsonData.data;
console.log(data_array.records[0].value)
--> should log 3
EXAMPLE HERE: http://codepen.io/theConstructor/pen/wGdpjq
So the problem might have been with SetState() in React, I was able to access the objects by pushing them first in an empty array:
var varArr = new Array();
for(key in this.state.data.records) {
if(this.state.data.records.hasOwnProperty(key)) {
var value = this.state.data.records[key];
varArr.push(value);
}
}
data_array is an Array. data.records in an Array. What are you expecting to see?
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