@mapwhit/style-expressions/lib/expression/scope.js

Process expressions in map style.

/**
 * Tracks `let` bindings during expression parsing.
 * @private
 */
export default class Scope {
  constructor(parent, bindings = []) {
    this.parent = parent;
    this.bindings = {};
    for (const [name, expression] of bindings) {
      this.bindings[name] = expression;
    }
  }

  concat(bindings) {
    return new Scope(this, bindings);
  }

  get(name) {
    if (this.bindings[name]) {
      return this.bindings[name];
    }
    if (this.parent) {
      return this.parent.get(name);
    }
    throw new Error(`${name} not found in scope.`);
  }

  has(name) {
    if (this.bindings[name]) return true;
    return this.parent ? this.parent.has(name) : false;
  }
}