Function copyPrologue

test/fixtures/snapshot/typescript.js:26999–27002

* Copies any necessary standard and custom prologue-directives into target array. * @param source origin statements array * @param target result statements array * @param ensureUseStrict boolean determining whether the function need to add prologue-directives * @p

(source, target, ensureUseStrict, visitor)

         * @param visitor Optional callback used to visit any custom prologue directives.
         */
        function copyPrologue(source, target, ensureUseStrict, visitor) {
            var offset = copyStandardPrologue(source, target, 0, ensureUseStrict);
            return copyCustomPrologue(source, target, offset, visitor);
        }
        function isUseStrictPrologue(node) {
            return ts.isStringLiteral(node.expression) && node.expression.text === "use strict";
        }