tools,lib: enable strict equality lint rule

Enablie a lint rule to require `===` and `!==` instead of `==` and `!=`
except in some well-defined cases:

* comparing against `null` as a shorthand for also checking for
  `undefined`
* comparing the result of `typeof`
* comparing literal values

In cases where `==` or `!=` are being used as optimizations, use an
ESLint comment to disable the `eqeqeq` rule for that line explicitly. I
rather like this because it's a signal that the usage is intentional and
not a mistake.

PR-URL: https://github.com/nodejs/node/pull/12446
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/buffer.js b/lib/buffer.js
index 9163eb17c8..87bdfd2d95 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -192,6 +192,7 @@ Buffer.allocUnsafeSlow = function(size) {
 // If --zero-fill-buffers command line argument is set, a zero-filled
 // buffer is returned.
 function SlowBuffer(length) {
+  // eslint-disable-next-line eqeqeq
   if (+length != length)
     length = 0;
   assertSize(+length);
@@ -306,7 +307,7 @@ function fromObject(obj) {
     return b;
   }
 
-  if (obj != undefined) {
+  if (obj != null) {
     if (obj.length !== undefined || isAnyArrayBuffer(obj.buffer)) {
       if (typeof obj.length !== 'number' || obj.length !== obj.length) {
         return new FastBuffer();