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React - send function props to Children

I saw some questions speaking about similar issues but somehow I still do not manage to solve my issue so here I am asking for your kind help. I am pretty new to React and would like to send a function from a Parent to a child and then use it from the Child but somehow when I want to use it it says
Uncaught TypeError: Cannot read property 'props' of undefined"
Edited Code after first answers were helping:
var Menu = React.createClass({
links : [
{key : 1, name : "help", click : this.props.changePageHelp}
],
render : function() {
var menuItem = this.links.map(function(link){
return (
<li key={link.key} className="menu-help menu-link" onClick={link.click}>{link.name}</li>
)
});
return (
<ul>
{menuItem}
</ul>
)
}
});
var Admin = React.createClass ({
_changePageHelp : function() {
console.log('help');
},
render : function () {
return (
<div>
<div id="menu-admin"><Menu changePageHelp={this._changePageHelp.bind(this)} /></div>
</div>
)
}
});
ReactDOM.render(<Admin />, document.getElementById('admin'));

Pass a value from Menu function and recieve it in the changePageHelp function and it works.
var Menu = React.createClass({
render : function() {
return (
<div>
{this.props.changePageHelp('Hello')}
</div>
)
}
});
var Admin = React.createClass ({
_changePageHelp : function(help) {
return help;
},
render : function () {
return (
<div>
<div id="menu-admin"><Menu changePageHelp={this._changePageHelp.bind(this)} /></div>
</div>
)
}
});
ReactDOM.render(<Admin />, document.getElementById('admin'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react-dom.min.js"></script>
<div id="admin"></div>

For performance reasons, you should avoid using bind or arrow functions in JSX props. This is because a copy of the event handling function is created for every instance generated by the map() function. This is explained here: https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-no-bind.md
To avoid this you can pull the repeated section into its own component. Here is a demo: http://codepen.io/PiotrBerebecki/pen/EgvjmZ The console.log() call in your parent component receives now the name of the link. You could use it for example in React Router.
var Admin = React.createClass ({
_changePageHelp : function(name) {
console.log(name);
},
render : function () {
return (
<div>
<div id="menu-admin">
<Menu changePageHelp={this._changePageHelp} />
</div>
</div>
);
}
});
var Menu = React.createClass({
getDefaultProps: function() {
return {
links: [
{key: 1, name: 'help'},
{key: 2, name: 'about'},
{key: 3, name: 'contact'}
]
};
},
render: function() {
var menuItem = this.props.links.map((link) => {
return (
<MenuItem key={link.key}
name={link.name}
changePageHelp={this.props.changePageHelp}
className="menu-help menu-link" />
);
});
return (
<ul>
{menuItem}
</ul>
);
}
});
var MenuItem = React.createClass ({
handleClick: function() {
this.props.changePageHelp(this.props.name);
},
render : function () {
return (
<li onClick={this.handleClick}>
Click me to console log in Admin component <b>{this.props.name}</b>
</li>
);
}
});
ReactDOM.render(<Admin />, document.getElementById('admin'));

ReactJS not able to reference state created

http://jsfiddle.net/adamchenwei/3rt0930z/20/
I just trying to create an example to learn how state works in a list.
What I intent to do is to allow a particular value that got repeated in a list, to change, in ALL items in the list, by using state. For example, in this case, I want to change all the list item's name to 'lalala' when I run changeName of onClick.
However I have this warning (issue at fiddle version 11, resolved at version 15)
Any help on resolving it to achieve purpose above?
Actual Code
var items = [
{ name: 'Believe In Allah', link: 'https://www.quran.com' },
{ name: 'Prayer', link: 'https://www.quran.com' },
{ name: 'Zakat', link: 'https://www.quran.com' },
{ name: 'Fasting', link: 'https://www.quran.com' },
{ name: 'Hajj', link: 'https://www.quran.com' },
];
var ItemModule = React.createClass({
getInitialState: function() {
return { newName: this.props.name }
},
changeName() {
console.log('changed name');
this.setState({ newName: 'lalala' });
},
render() {
//<!-- <a className='button' href={this.props.link}>{this.props.name}</a> -->
return (
<li onClick={this.changeName}>
{this.state.newName}
</li>
);
}
});
var RepeatModule = React.createClass({
getInitialState: function() {
return { items: [] }
},
render: function() {
var listItems = this.props.items.map(function(item) {
return (
<div>
<ItemModule
key={item.name}
name={item.name} />
</div>
);
});
return (
<div className='pure-menu'>
<h3>Islam Pillars</h3>
<ul>
{listItems}
</ul>
</div>
);
}
});
ReactDOM.render(<RepeatModule items={items} />,
document.getElementById('react-content'));
-UPDATE-
fiddle version 16
updated fidle, now there is issue with key, also, the onClick did not update the value for all the list item. Is there something wrong I did?
-UPDATE-
fiddle version 20
Now the only issue is change all the list item's name to 'lalala' when I run changeName of onClick.

remove the parenthesis from
onClick={this.changeName()},
so
onClick={this.changeName}
you want to call the function onClick, but you are calling it on render that way

I think you meant to do onClick={this.changeName}
In the way you have it you are calling the changeName function on render instead of on click.

Reactjs possible to change onclick function name like changing props

Possible to change onclick function like changing props, like changing 'props message' to 'new message' ?
For example:
var SmallMessageBox = React.createClass({
getDefaultProps: function() {
return {
message: 'props message',
onClick: 'this.eventHandler_Two'
}
},
eventHandler_One: function(){
console.log('event1');
},
eventHandler_Two: function(){
console.log('event2');
},
render: function(){
return (
<div>
<small>{this.props.message}</small>
<button onClick={this.eventHandler_One}>button</button>
</div>
);
}
});
React.render(
<SmallMessageBox message="new message" onClick="new onClick function for event2" />, document.getElementById('react-container'),
function(){
console.log('after render');
}
);

Yes, components can be supplied with properties of type function. You can either bind event handlers directly to functions passed through props or do something in your internal component method, before executing the prop function. Please note, that you cannot change definition of supplied function, once target component was initialized, it will not be updated.
Also, in many cases you must use bind on your passed in function to maintain proper context.
Here's how it should look like in accordance with your example:
var SmallMessageBox = React.createClass({
propTypes: {
message: React.PropTypes.string.isRequired,
onClick: React.PropTypes.func
},
getDefaultProps: function() {
return {
message: 'props message',
onClick: function() {
console.log("I will be executed, only if props.onClick was not specified");
}
}
},
eventHandler: function() {
},
render: function() {
return (
<div>
<small>{this.props.message}</small>
<button onClick={ this.props.onClick }>button</button>
</div>
);
}
});
React.render(
<SmallMessageBox onClick={function() { console.log( "remove me to get the other console.log"); }} message="new message"/>, document.getElementById('react-container'),
function(){
console.log('after render');
}
);
I would also encourage you to implicitly specify your props with their type. You can find more information here.

Unable to update state within componentWillReceiveProps method

I have a component which is updated by a parent component by passing a prop. Within the componentWillReceiveProps i would like to change a state (availableData) which contains the newly added data from the prop (newData).
The prop is named newData, and the state which is updated is named availableData.
When i attempt to access the availableData where i concatenate new (unique) data i get following error:
Uncaught TypeError: Cannot read property 'availableData' of undefinedInline JSX script:79
And the code snippet:
var DataList = React.createClass({
getInitialState: function() {
return {availableData: []};
},
componentWillReceiveProps: function(nextProps) {
var availableData = this.state.availableData;
var newData = nextProps.newData;
if (_.isEmpty(availableData)) {
this.setState({availableData: nextProps.newData});
} else {
_.each(newData, function(_newData) {
var isDuplicate = false;
_.each(availableData, function(_availableData) {
if(isSameData(_availableData, _newData)) {
isDuplicate = true;
}
});
if (!isDuplicate) {
console.log(_newData);
this.setState({ availableData: this.state.availableData.concat([_newData]) });
}
});
}
},
handleClick: function (_data) {
},
render: function() {
var dataItems = this.state.availableData.map(function (_data, index) {
return <DataItem data={_data} key={index} onClick={this.handleClick.bind(this, _data)} />;
}, this);
return (
<div className="col-lg-3">
<ul className="list-group">
<li className="list-group-item active">Data</li>
{dataItems}
</ul>
</div>
);
}
});
Failing on:
this.setState({ availableData: this.state.availableData.concat([_newData]) });
UPDATE:
Solved by setting var _this = this; outside the loop and referring to _this, unfortunately all setStates are not being initialized.

this isn't the component in the context of your duplicate. You need to pass the outer most this to your _.each.
_.each(list, iteratee, [context])

Reactjs managing stateful children

I have a dynamic list of children, that are form inputs.
ex:
var FormRows = React.createClass({
getInitialState: function() {
return {
rows: []
}
},
createRows: function() {
this.props.values.maps(value){
rows.push(<FormRow ...handlers... ...props... value={value} />
}
},
addNewRow{
// add a new row
},
render: function() {
return (
<div>
{this.state.rows}
</div>
);
});
var FormRow = React.createClass({
getInitialState: function() {
return {
value: this.props.value || null
}
},
render: function() {
<input type='text' defaultValue={this.state.value} ...changeHandler ... }
}
});
This is a dumbed down version , but the idea, is a its a dynamic form, where the user can click a plus button to add a row, and a minus button, which will set the row to visibility to hidden.
This state is nested n levels deep. What is the best way to actually get the state out of the children, and submit the form? I can use 'ref' add a function to getFormValue(): { return this.state.value } to the FormRow button, but i'm not sure if thats the best practice way.
I find myself using this pattern quite often, an array of undetermined size of children, that need to pass the state up.
Thanks

It’s not a dumb question at all, and a good example of using flux principals in React. Consider something like this:
var App
// The "model"
var Model = {
values: ['foo', 'bar'],
trigger: function() {
App.forceUpdate()
console.log(this.values)
},
update: function(value, index) {
this.values[index] = value
this.trigger()
},
add: function() {
this.values.push('New Row')
this.trigger()
}
}
var FormRows = React.createClass({
addRow: function() {
Model.add()
},
submit: function() {
alert(Model.values);
},
render: function() {
var rows = Model.values.map(function(value, index) {
return <FormRow key={index} onChange={this.onChange} index={index} value={value} />
}, this)
return (
<div>{rows}<button onClick={this.addRow}>Add row</button><button onClick={this.submit}>Submit form</button></div>
)
}
})
var FormRow = React.createClass({
onChange: function(e) {
Model.update(e.target.value, this.props.index)
},
render: function() {
return <input type='text' defaultValue={this.props.value} onChange={this.onChange} />
}
});
App = React.render(<FormRows />, document.body)
I used a simplified model/event example using Array and forceUpdate but the point here is to let the model "own" the form data. The child components can then make API calls on that model and trigger a re-render of the entire App with the new data (Flux).
Then just use the model data on submit.
Demo: http://jsfiddle.net/ekr41bzr/

Bind values of inputs to some model (for example build in Backbone or Flux) and on submit retrieve values from there, without touching inputs.