samdash

samdash.js

function head(xs) {
  return xs[0];
}

function last(xs) {
  return xs[xs.length - 1];
}

function init(xs) {
  return xs.slice(0, xs.length - 1);
}

function tail(xs) {
  return xs.slice(1, xs.length);
}

function reduce(xs, f, acc) {
  switch (xs.constructor) {
    case Array:
      return reduceArray(xs, f, acc);

    case Object:
      return reduceObject(xs, f, acc);

    default:
      throw new TypeError('nah');
      break;
  }
}

function reduceArray(xs, f, acc) {
  for (var i = 0; i < xs.length; i++) {
    acc = f(acc, xs[i], i);
  }

  return acc;
}

function reduceObject(obj, f, acc) {
  var keys = Object.keys(obj);
  
  for (var i = 0; i < keys.length; i++) {
    var key = keys[i];
    acc = f(acc, obj[key], key);
  }

  return acc;
}

function scan(xs, f, acc) {
  var result = [];

  for (var i = 0; i < xs.length; i++) {
    acc = result[result.push(f(acc, xs[i])) - 1];
  }

  return result;
}

function map(xs, f) {
  return reduce(xs, function(acc, x, i) {
    return acc.concat(f(x, i));
  }, []);
}

function filter(xs, f) {
  return reduce(xs, function(acc, x, i) {
    return f(x, i) ? acc.concat(x) : acc;
  }, []);
}

function some(xs, f) {
  return reduce(xs, function(acc, x, i) {
    return f(x, i) ? true : acc;
  }, false);
}

function every(xs, f) {
  return reduce(xs, function(acc, x, i) {
    return f(x, i) ? acc : false;
  }, true);
}

function intersperse(xs, a) {
  return init(reduce(xs, function(acc, x) {
    return acc.concat([x, a]);
  }, []));
}

function flatten(xs) {
  if (xs.constructor === Array) {
    return reduce(xs, function(acc, x) {
      return acc.concat(flatten(x));
    }, []);
  }

  return xs;
}

function forEach(xs, f) {
  for (var i = 0; i < xs.length; i++) {
    f(xs[i], i);
  }
}