timers: Fail early when callback is not a function

doc/api/timers.markdown

@@ -37,6 +37,8 @@ The entire callback queue is processed every event loop iteration. If you queue
 an immediate from inside an executing callback, that immediate won't fire
 until the next event loop iteration.
 
+If `callback` is not a function `setImmediate()` will throw immediately.
+
 ## setInterval(callback, delay[, arg][, ...])
 
 To schedule the repeated execution of `callback` every `delay` milliseconds.
@@ -47,6 +49,8 @@ To follow browser behavior, when using delays larger than 2147483647
 milliseconds (approximately 25 days) or less than 1, Node.js will use 1 as the
 `delay`.
 
+If `callback` is not a function `setInterval()` will throw immediately.
+
 ## setTimeout(callback, delay[, arg][, ...])
 
 To schedule execution of a one-time `callback` after `delay` milliseconds. Returns a
@@ -62,6 +66,8 @@ To follow browser behavior, when using delays larger than 2147483647
 milliseconds (approximately 25 days) or less than 1, the timeout is executed
 immediately, as if the `delay` was set to 1.
 
+If `callback` is not a function `setTimeout()` will throw immediately.
+
 ## unref()
 
 The opaque value returned by [`setTimeout`][] and [`setInterval`][] also has the method

lib/timers.js

@@ -177,6 +177,10 @@ exports.enroll = function(item, msecs) {
 
 
 exports.setTimeout = function(callback, after) {
+  if (typeof callback !== 'function') {
+    throw new TypeError('"callback" argument must be a function');
+  }
+
   after *= 1; // coalesce to number or NaN
 
   if (!(after >= 1 && after <= TIMEOUT_MAX)) {
@@ -233,6 +237,10 @@ exports.clearTimeout = function(timer) {
 
 
 exports.setInterval = function(callback, repeat) {
+  if (typeof callback !== 'function') {
+    throw new TypeError('"callback" argument must be a function');
+  }
+
   repeat *= 1; // coalesce to number or NaN
 
   if (!(repeat >= 1 && repeat <= TIMEOUT_MAX)) {
@@ -419,6 +427,10 @@ Immediate.prototype._idlePrev = undefined;
 
 
 exports.setImmediate = function(callback, arg1, arg2, arg3) {
+  if (typeof callback !== 'function') {
+    throw new TypeError('"callback" argument must be a function');
+  }
+
   var i, args;
   var len = arguments.length;
   var immediate = new Immediate();

test/parallel/test-timers-throw-when-cb-not-function.js

@@ -0,0 +1,62 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+function doSetTimeout(callback, after) {
+  return function() {
+    setTimeout(callback, after);
+  };
+}
+
+assert.throws(doSetTimeout('foo'),
+  /"callback" argument must be a function/);
+assert.throws(doSetTimeout({foo: 'bar'}),
+  /"callback" argument must be a function/);
+assert.throws(doSetTimeout(),
+  /"callback" argument must be a function/);
+assert.throws(doSetTimeout(undefined, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetTimeout(null, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetTimeout(false, 0),
+  /"callback" argument must be a function/);
+
+
+function doSetInterval(callback, after) {
+  return function() {
+    setInterval(callback, after);
+  };
+}
+
+assert.throws(doSetInterval('foo'),
+  /"callback" argument must be a function/);
+assert.throws(doSetInterval({foo: 'bar'}),
+  /"callback" argument must be a function/);
+assert.throws(doSetInterval(),
+  /"callback" argument must be a function/);
+assert.throws(doSetInterval(undefined, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetInterval(null, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetInterval(false, 0),
+  /"callback" argument must be a function/);
+
+
+function doSetImmediate(callback, after) {
+  return function() {
+    setImmediate(callback, after);
+  };
+}
+
+assert.throws(doSetImmediate('foo'),
+  /"callback" argument must be a function/);
+assert.throws(doSetImmediate({foo: 'bar'}),
+  /"callback" argument must be a function/);
+assert.throws(doSetImmediate(),
+  /"callback" argument must be a function/);
+assert.throws(doSetImmediate(undefined, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetImmediate(null, 0),
+  /"callback" argument must be a function/);
+assert.throws(doSetImmediate(false, 0),
+  /"callback" argument must be a function/);