所以說(shuō)到正則表達(dá)式我javascript，我只知道1%左右。我正在嘗試編寫一些代碼來(lái)檢測(cè)數(shù)學(xué)表達(dá)式（例如 2 + 3）。前段時(shí)間我在另一個(gè)問(wèn)題上發(fā)現(xiàn)了這個(gè)：/(?:(?:^|[-+_*/])(?:\s*-?\d+(\.\d+)?(?:[eE][+-]?\d+)?\s*))+$/I這似乎工作正常，但我只希望它在前面有特定關(guān)鍵字時(shí)工作。所以現(xiàn)在我有這樣的東西：var re = /(?:(?:^|[-+_*/])(?:\s*-?\d+(\.\d+)?(?:[eE][+-]?\d+)?\s*))+$/i;var str = "2 + 2";console.log(str.match(re));但我想要這個(gè)：var keyword = "Some keyword ";var str = `${keyword}2 + 2`;//Regular expressio that should only work if "Some keyword" and math expression are therevar re = //the expression//should match the stringconsole.log(str.match(re));//But if the keiword is not therevar keyword = "";var str = `${keyword}2 + 2`;//Regular expressio that should only work if "Some keyword" and math expression are therevar re = //the expression//should NOT match the stringconsole.log(str.match(re));我試過(guò)這個(gè)，但它并沒(méi)有真正達(dá)到我的預(yù)期：var one = /Some keyword /i;var two = /(?:(?:^|[-+_*/])(?:\s*-?\d+(\.\d+)?(?:[eE][+-]?\d+)?\s*))+$/i;var one_or_two = new RegExp("(" + one.source + ")?(" + two.source + ")")var str = "Some keyword 2 + 1";alert(str.match(one_or_two))我需要在正則表達(dá)式中使用所有這些，因?yàn)槲也荒苁褂?str.match(re)有沒(méi)有辦法做到這一點(diǎn)？無(wú)論如何提前感謝。