Using the append() method in d3 with a function argument adds new

Question

Using the append() method in d3 with a function argument adds new

This is functional code:

// A
d3.select("body").selectAll(".testDiv")
  .data(["div1", "div2", "div3"])
  .enter().append("div")
    .classed("testDiv", true)
    .text(function(d) { return d; });

The next snippet is essentially the same, except that instead of using "div" as an argument for append, a function(d) is used to simply return "div":

// B
d3.select("body").selectAll(".testDiv")
  .data(["div1", "div2", "div3"])
  .enter().append(function(d) { return "div"; })
    .classed("testDiv", true)
   .text(function(d) { return d; });

However, B does not function properly and results in the error message "Uncaught TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'."

What is the difference between using "div" as an argument for append() versus function(d) { return "div"; }?

javascript d3.js

Answer 1

Answer №1

Simply put, when using the append method with a function as an argument, the function must return a DOM element. The append method's documentation specifies:

The name can be specified as either a constant string or a function that returns the DOM element to append.

An example of valid usage of append with a function is:

.append(function() { return document.createElement('div');});

Conversely, the following code snippet would be considered invalid since it does not return a DOM element:

.append(function() { return 'div';});

The rationale behind this requirement becomes apparent when examining the source code provided:

  d3_selectionPrototype.append = function(name) {
    name = d3_selection_creator(name);
    return this.select(function() {
      return this.appendChild(name.apply(this, arguments));
    });
  };

  function d3_selection_creator(name) {
    function create() {
      var document = this.ownerDocument, namespace = this.namespaceURI;
      return namespace ? document.createElementNS(namespace, name) : document.createElement(name);
    }
    function createNS() {
      return this.ownerDocument.createElementNS(name.space, name.local);
    }
    return typeof name === "function" ? name : (name = d3.ns.qualify(name)).local ? createNS : create;
  }

When

typeof name === "function"

is true, the create or createNS functions are never invoked. Since appendChild only accepts a DOM element, the function passed to append must ultimately resolve to a DOM element.

Answer 2

Simply put, when using the append method with a function as an argument, the function must return a DOM element. The append method's documentation specifies:

The name can be specified as either a constant string or a function that returns the DOM element to append.

An example of valid usage of append with a function is:

.append(function() { return document.createElement('div');});

Conversely, the following code snippet would be considered invalid since it does not return a DOM element:

.append(function() { return 'div';});

The rationale behind this requirement becomes apparent when examining the source code provided:

  d3_selectionPrototype.append = function(name) {
    name = d3_selection_creator(name);
    return this.select(function() {
      return this.appendChild(name.apply(this, arguments));
    });
  };

  function d3_selection_creator(name) {
    function create() {
      var document = this.ownerDocument, namespace = this.namespaceURI;
      return namespace ? document.createElementNS(namespace, name) : document.createElement(name);
    }
    function createNS() {
      return this.ownerDocument.createElementNS(name.space, name.local);
    }
    return typeof name === "function" ? name : (name = d3.ns.qualify(name)).local ? createNS : create;
  }

When

typeof name === "function"

is true, the create or createNS functions are never invoked. Since appendChild only accepts a DOM element, the function passed to append must ultimately resolve to a DOM element.

Answer 3

Answer №2

In order to include a conditional statement within the .append() function, it is crucial to ensure that there is a return value for every possible case.

You cannot selectively choose to append a div element; it must be returned consistently to avoid encountering errors.

For instance, the following code snippet will not succeed:

.append(function(d) { 
  if(sometimesTrue) {
    return document.createElement('div');
  }
});

An else {} statement is necessary to provide an alternative DOM element for the correct functionality of .append().

This issue was observed in D3.v3, so it may have been addressed in newer versions. Hopefully, this information proves helpful to someone.

Answer 4

In order to include a conditional statement within the .append() function, it is crucial to ensure that there is a return value for every possible case.

You cannot selectively choose to append a div element; it must be returned consistently to avoid encountering errors.

For instance, the following code snippet will not succeed:

.append(function(d) { 
  if(sometimesTrue) {
    return document.createElement('div');
  }
});

An else {} statement is necessary to provide an alternative DOM element for the correct functionality of .append().

This issue was observed in D3.v3, so it may have been addressed in newer versions. Hopefully, this information proves helpful to someone.

Using the append() method in d3 with a function argument adds new

Answer №1

Answer №2

Similar questions

List item with React Material UI tooltip

React functional components can utilize switch cases for conditional logic

Determining the height of the first element in jQuery

Can you provide me with some insight on the process of iterating through an object utilizing the

React and Redux Toolkit collaborated to create a seamless shared state management system,

My selection of jQuery multiselect is experiencing issues with enabling disabled options

Guide to sorting data by the status value within a JavaScript object?

Maximizing Input Field Utility in React JS

I have managed to update the Immutable and Primitive Data-Types in JS. Now, the question arises - are these truly Primitives or are the concepts in

Should data validations be implemented on both the client-side and server-side for optimal security and accuracy?

Why does one image render while the other with the same src does not?

Encountered an uncaughtException in Node.js and mongoDB: User model cannot be overwritten once compiled

What is the method for storing elements in localStorage within a ReactJs application?

A step-by-step guide on modifying the box-shadow color using jquery

Refresh the Kendo Auto Complete feature within a grid whenever the grid page is changed

Having trouble retrieving multiple selected values from the paper listbox in Polymer 3

Transferring a JavaScript variable to PHP using AJAX does not display any output

Issue with prop inheritance in componentInheritance problem with passing props to

Preventing SQL Injection by properly formatting SQL queries

Reset the checked state in React JSX to false by using a reset button