--- /dev/null
+var baseIndexOf = require('./baseIndexOf');
+
+/**
+ * Used by `_.trim` and `_.trimStart` to get the index of the first string symbol
+ * that is not found in the character symbols.
+ *
+ * @private
+ * @param {Array} strSymbols The string symbols to inspect.
+ * @param {Array} chrSymbols The character symbols to find.
+ * @returns {number} Returns the index of the first unmatched string symbol.
+ */
+function charsStartIndex(strSymbols, chrSymbols) {
+ var index = -1,
+ length = strSymbols.length;
+
+ while (++index < length && baseIndexOf(chrSymbols, strSymbols[index], 0) > -1) {}
+ return index;
+}
+
+module.exports = charsStartIndex;