diff options
Diffstat (limited to 'node_modules/es-abstract/2017/AdvanceStringIndex.js')
-rw-r--r-- | node_modules/es-abstract/2017/AdvanceStringIndex.js | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/node_modules/es-abstract/2017/AdvanceStringIndex.js b/node_modules/es-abstract/2017/AdvanceStringIndex.js new file mode 100644 index 000000000..666f578b1 --- /dev/null +++ b/node_modules/es-abstract/2017/AdvanceStringIndex.js @@ -0,0 +1,45 @@ +'use strict'; + +var GetIntrinsic = require('../GetIntrinsic'); + +var IsInteger = require('./IsInteger'); +var Type = require('./Type'); + +var MAX_SAFE_INTEGER = require('../helpers/maxSafeInteger'); + +var $TypeError = GetIntrinsic('%TypeError%'); + +var $charCodeAt = require('../helpers/callBound')('String.prototype.charCodeAt'); + +// https://ecma-international.org/ecma-262/6.0/#sec-advancestringindex + +module.exports = function AdvanceStringIndex(S, index, unicode) { + if (Type(S) !== 'String') { + throw new $TypeError('Assertion failed: `S` must be a String'); + } + if (!IsInteger(index) || index < 0 || index > MAX_SAFE_INTEGER) { + throw new $TypeError('Assertion failed: `length` must be an integer >= 0 and <= 2**53'); + } + if (Type(unicode) !== 'Boolean') { + throw new $TypeError('Assertion failed: `unicode` must be a Boolean'); + } + if (!unicode) { + return index + 1; + } + var length = S.length; + if ((index + 1) >= length) { + return index + 1; + } + + var first = $charCodeAt(S, index); + if (first < 0xD800 || first > 0xDBFF) { + return index + 1; + } + + var second = $charCodeAt(S, index + 1); + if (second < 0xDC00 || second > 0xDFFF) { + return index + 1; + } + + return index + 2; +}; |