Sweet.js - set default

sweet.setd.sjs.js

syntax setd = (ctx) => {
  const dummy = #`dummy`.get(0);

  let result = #``;

  ctx.expand('expr');
  ctx.reset();

  const selectors = [];

  let next = ctx.next().value;

  while (!next.isPunctuator('=')) {
    selectors.push(next);
    next = ctx.next().value;
  }

  const operator = next;

  if (!operator.isPunctuator('=')) {
    throw new Error(`unknown syntax: "${operator}". Must be "="`);
  }

  selectors.forEach((selector) => {
    if (!(selector.isPunctuator('.')
      || selector.isBrackets()
      || selector.isIdentifier()
    )) {
      throw new Error(`unknown syntax: "${selector}"`);
    }
  });

  const exprValue = ctx.next().value;

  if (selectors.length > 1) {
    const len = selectors.length;
    for (let i = 0; i < len - 2; i++) {
      const otherSlectors = selectors
        .slice(0, i + 1);

      const nextSelector = selectors[i + 1];
      if (nextSelector.isPunctuator('.')) {
        result = result.concat(#`
        if (${otherSlectors} == null) {
          ${otherSlectors} = {};
        }
        `);
      } else if (nextSelector.isBrackets()) {
        result = result.concat(#`
        if (${otherSlectors} == null) {
          ${otherSlectors} = [];
        }
        `);
      }
    }
  }

  return result.concat(#`
  if (${selectors} == null) {
    ${selectors} = ${exprValue}
  }
  `);
}


function test(options) {
  setd options.deep.deep.deep.c = { text: 'hello there C' };

  return JSON.stringify(options, true, 2);
}

console.log(test({
  deep: {
    a: 1
  }
}));