swig/lib/tags/if.js

A simple, powerful, and extendable templating engine for node.js and browsers, similar to Django, Jinja2, and Twig.

/**
 * Used to create conditional statements in templates. Accepts most JavaScript valid comparisons.
 *
 * Can be used in conjunction with <a href="#elseif"><code data-language="swig">{% elseif ... %}</code></a> and <a href="#else"><code data-language="swig">{% else %}</code></a> tags.
 *
 * @alias if
 *
 * @example
 * {% if x %}{% endif %}
 * {% if !x %}{% endif %}
 * {% if not x %}{% endif %}
 *
 * @example
 * {% if x and y %}{% endif %}
 * {% if x && y %}{% endif %}
 * {% if x or y %}{% endif %}
 * {% if x || y %}{% endif %}
 * {% if x || (y && z) %}{% endif %}
 *
 * @example
 * {% if x [operator] y %}
 *   Operators: ==, !=, <, <=, >, >=, ===, !==
 * {% endif %}
 *
 * @example
 * {% if x == 'five' %}
 *   The operands can be also be string or number literals
 * {% endif %}
 *
 * @example
 * {% if x|lower === 'tacos' %}
 *   You can use filters on any operand in the statement.
 * {% endif %}
 *
 * @example
 * {% if x in y %}
 *   If x is a value that is present in y, this will return true.
 * {% endif %}
 *
 * @param {...mixed} conditional Conditional statement that returns a truthy or falsy value.
 */
exports.compile = function (compiler, args, content, parents, options, blockName) {
  return 'if (' + args.join(' ') + ') { \n' +
    compiler(content, parents, options, blockName) + '\n' +
    '}';
};

exports.parse = function (str, line, parser, types) {
  if (typeof str === "undefined") {
    throw new Error('No conditional statement provided on line ' + line + '.');
  }

  parser.on(types.COMPARATOR, function (token) {
    if (this.isLast) {
      throw new Error('Unexpected logic "' + token.match + '" on line ' + line + '.');
    }
    if (this.prevToken.type === types.NOT) {
      throw new Error('Attempted logic "not ' + token.match + '" on line ' + line + '. Use !(foo ' + token.match + ') instead.');
    }
    this.out.push(token.match);
    this.filterApplyIdx.push(this.out.length);
  });

  parser.on(types.NOT, function (token) {
    if (this.isLast) {
      throw new Error('Unexpected logic "' + token.match + '" on line ' + line + '.');
    }
    this.out.push(token.match);
  });

  parser.on(types.BOOL, function (token) {
    this.out.push(token.match);
  });

  parser.on(types.LOGIC, function (token) {
    if (!this.out.length || this.isLast) {
      throw new Error('Unexpected logic "' + token.match + '" on line ' + line + '.');
    }
    this.out.push(token.match);
    this.filterApplyIdx.pop();
  });

  return true;
};

exports.ends = true;