feat: pull constants into separate file

src/constants.js

@@ -0,0 +1,27 @@
+// package version used in the ix-lib parameter
+export const VERSION = '2.3.2';
+// regex pattern used to determine if a domain is valid
+export const DOMAIN_REGEX = /^(?:[a-z\d\-_]{1,62}\.){0,125}(?:[a-z\d](?:\-(?=\-*[a-z\d])|[a-z]|\d){0,62}\.)[a-z\d]{1,63}$/i;
+// minimum generated srcset width
+export const MIN_SRCSET_WIDTH = 100;
+// maximum generated srcset width
+export const MAX_SRCSET_WIDTH = 8192;
+// default tolerable percent difference between srcset pair widths
+export const DEFAULT_SRCSET_WIDTH_TOLERANCE = .08;
+
+// default quality parameter values mapped by each dpr srcset entry
+export const DPR_QUALITIES = {
+  1: 75,
+  2: 50,
+  3: 35,
+  4: 23,
+  5: 20
+};
+
+export const DEFAULTS = {
+  domain: null,
+  useHTTPS: true,
+  includeLibraryParam: true,
+  urlPrefix: 'https://',
+  secureURLToken: null,
+};