tty: add hasColors function

This adds a small wrapper around the `getColorDepth` function to check
if the stream supports at least a specific amount of colors. This is
convenient as the other API is not as straight forward and most use
cases likely only want to know if a specific amount of colors is
supported or not.

PR-URL: https://github.com/nodejs/node/pull/26247
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/lib/internal/tty.js b/lib/internal/tty.js
index 45f278d542..486dbbeaa5 100644
--- a/lib/internal/tty.js
+++ b/lib/internal/tty.js
@@ -22,6 +22,11 @@
 
 'use strict';
 
+const {
+  ERR_INVALID_ARG_TYPE,
+  ERR_OUT_OF_RANGE
+} = require('internal/errors').codes;
+
 let OSRelease;
 
 const COLORS_2 = 1;
@@ -151,6 +156,23 @@ function getColorDepth(env = process.env) {
   return COLORS_2;
 }
 
+function hasColors(count, env) {
+  if (env === undefined &&
+      (count === undefined || typeof count === 'object' && count !== null)) {
+    env = count;
+    count = 16;
+  } else {
+    if (typeof count !== 'number') {
+      throw new ERR_INVALID_ARG_TYPE('count', 'number', count);
+    }
+    if (count < 2) {
+      throw new ERR_OUT_OF_RANGE('count', '>= 2', count);
+    }
+  }
+  return count <= 2 ** getColorDepth(env);
+}
+
 module.exports = {
-  getColorDepth
+  getColorDepth,
+  hasColors
 };