getformat url context defaultgetformat

Note: The loaders API is being redesigned. This hook may disappear or its signature may change. Do not rely on the API described below.

• url {string}
• context {Object}
• defaultGetFormat {Function}
• Returns: {Object}
  • format {string}

The getFormat hook provides a way to define a custom method of determining how a URL should be interpreted. The format returned also affects what the acceptable forms of source values are for a module when parsing. This can be one of the following:

Note: These types all correspond to classes defined in ECMAScript.

• The specific [ArrayBuffer][] object is a [SharedArrayBuffer][].
• The specific [TypedArray][] object is a [Uint8Array][].

Note: If the source value of a text-based format (i.e., 'json', 'module') is not a string, it is converted to a string using [util.TextDecoder][].

/**
 * @param {string} url
 * @param {Object} context (currently empty)
 * @param {Function} defaultGetFormat
 * @returns {Promise<{ format: string }>}
 */
export async function getFormat(url, context, defaultGetFormat) {
  if (Math.random() > 0.5) { // Some condition.
    // For some or all URLs, do some custom logic for determining format.
    // Always return an object of the form {format: <string>}, where the
    // format is one of the strings in the preceding table.
    return {
      format: 'module',
    };
  }
  // Defer to Node.js for all other URLs.
  return defaultGetFormat(url, context, defaultGetFormat);
}