Expandable object tree view

React, Components, Object, State, Recursion · Nov 16, 2020

Renders a tree view of a JSON object or array with collapsible content.

Use the value of the toggled prop to determine the initial state of the content (collapsed/expanded).
Use the useState() hook to create the isToggled state variable and give it the value of the toggled prop initially.
Render a <span> element and bind its onClick event to alter the component's isToggled state.
Determine the appearance of the component, based on isParentToggled, isToggled, name and checking for Array.isArray() on data.
For each child in data, determine if it is an object or array and recursively render a sub-tree or a text element with the appropriate style.

.tree-element {
  margin: 0 0 0 4px;
  position: relative;
}

.tree-element.is-child {
  margin-left: 16px;
}

div.tree-element::before {
  content: '';
  position: absolute;
  top: 24px;
  left: 1px;
  height: calc(100% - 48px);
  border-left: 1px solid gray;
}

p.tree-element {
  margin-left: 16px;
}

.toggler {
  position: absolute;
  top: 10px;
  left: 0px;
  width: 0;
  height: 0;
  border-top: 4px solid transparent;
  border-bottom: 4px solid transparent;
  border-left: 5px solid gray;
  cursor: pointer;
}

.toggler.closed {
  transform: rotate(90deg);
}

.collapsed {
  display: none;
}

const TreeView = ({
  data,
  toggled = true,
  name = null,
  isLast = true,
  isChildElement = false,
  isParentToggled = true
}) => {
  const [isToggled, setIsToggled] = React.useState(toggled);
  const isDataArray = Array.isArray(data);

  return (
    <div
      className={`tree-element ${isParentToggled && 'collapsed'} ${
        isChildElement && 'is-child'
      }`}
    >
      <span
        className={isToggled ? 'toggler' : 'toggler closed'}
        onClick={() => setIsToggled(!isToggled)}
      />
      {name ? <strong>&nbsp;&nbsp;{name}: </strong> : <span>&nbsp;&nbsp;</span>}
      {isDataArray ? '[' : '{'}
      {!isToggled && '...'}
      {Object.keys(data).map((v, i, a) =>
        typeof data[v] === 'object' ? (
          <TreeView
            key={`${name}-${v}-${i}`}
            data={data[v]}
            isLast={i === a.length - 1}
            name={isDataArray ? null : v}
            isChildElement
            isParentToggled={isParentToggled && isToggled}
          />
        ) : (
          <p
            key={`${name}-${v}-${i}`}
            className={isToggled ? 'tree-element' : 'tree-element collapsed'}
          >
            {isDataArray ? '' : <strong>{v}: </strong>}
            {data[v]}
            {i === a.length - 1 ? '' : ','}
          </p>
        )
      )}
      {isDataArray ? ']' : '}'}
      {!isLast ? ',' : ''}
    </div>
  );
};

const data = {
  lorem: {
    ipsum: 'dolor sit',
    amet: {
      consectetur: 'adipiscing',
      elit: [
        'duis',
        'vitae',
        {
          semper: 'orci'
        },
        {
          est: 'sed ornare'
        },
        'etiam',
        ['laoreet', 'tincidunt'],
        ['vestibulum', 'ante']
      ]
    },
    ipsum: 'primis'
  }
};
ReactDOM.createRoot(document.getElementById('root')).render(
  <TreeView data={data} name="data" />
);

Written by Angelos Chalaris

I'm Angelos Chalaris, a JavaScript software engineer, based in Athens, Greece. The best snippets from my coding adventures are published here to help others learn to code.

If you want to keep in touch, follow me on GitHub.

Expandable object tree view

Written by Angelos Chalaris

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