Whats the best way to update an object in an array in ReactJS?

Question

If you have an array as part of your state, and that array contains objects, whats an easy way to update the state with a change to one of those objects?

Example, modified from the tutorial on react:

var CommentBox = React.createClass({   getInitialState: function() {     return {data: [       { id: 1, author: "john", text: "foo" },       { id: 2, author: "bob", text: "bar" }     ]};   },   handleCommentEdit: function(id, text) {     var existingComment = this.state.data.filter({ function(c) { c.id == id; }).first();     var updatedComments = ??; // not sure how to do this        this.setState({data: updatedComments});   } } 

Answer 1

I quite like doing this with Object.assign rather than the immutability helpers.

handleCommentEdit: function(id, text) {     this.setState({       data: this.state.data.map(el => (el.id === id ? Object.assign({}, el, { text }) : el))     }); } 

I just think this is much more succinct than splice and doesn't require knowing an index or explicitly handling the not found case.

If you are feeling all ES2018, you can also do this with spread instead of Object.assign

this.setState({   data: this.state.data.map(el => (el.id === id ? {...el, text} : el)) }); 

Answer 2

While updating state the key part is to treat it as if it is immutable. Any solution would work fine if you can guarantee it.

Here is my solution using immutability-helper:

jsFiddle:

  var update = require('immutability-helper');    handleCommentEdit: function(id, text) {     var data = this.state.data;     var commentIndex = data.findIndex(function(c) {          return c.id == id;      });      var updatedComment = update(data[commentIndex], {text: {$set: text}});           var newData = update(data, {         $splice: [[commentIndex, 1, updatedComment]]     });     this.setState({data: newData});   }, 

Following questions about state arrays may also help:

• Correct modification of state arrays in ReactJS
• what is the preferred way to mutate a React state?