Sometimes, you might need to generate all partial substrings of a string. This might come in handy in a variety of situations, such as string matching, or string compression. Luckily, using JavaScript’s generator functions, this is a fairly simple task.
Left substring generator
Using a for...in loop, we can iterate over the string, and yield each substring, starting at the beginning. We can use String.prototype.slice() to get the substring. In order to terminate early, we can use String.prototype.length to check if the string is empty.
代码实现
const leftSubstrGenerator = function* (str) {
if (!str.length) return;
for (let i in str) yield str.slice(0, i + 1);
};
[...leftSubstrGenerator('hello')];
// [ 'h', 'he', 'hel', 'hell', 'hello' ]Right substring generator
The exact same technique with a for...in loop can be used when starting at the end of the string. Same as before, albeit with a slight modification, we can use String.prototype.slice() to get the substring. And again, we use String.prototype.length to terminate early if the string is empty.
使用样例
const rightSubstrGenerator = function* (str) {
if (!str.length) return;
for (let i in str) yield str.slice(-i - 1);
};
[...rightSubstrGenerator('hello')];
// [ 'o', 'lo', 'llo', 'ello', 'hello' ]翻译自：https://www.30secondsofcode.org/js/s/substring-generator
