所以，我正在研究一些运动问题。我的代码似乎工作正常，直到我决定循环遍历字符串来替换任何句子的任何实例。由于某种原因，循环不起作用。我想它不会以某种方式调用它，但我不知道如何调用循环。我认为循环会自动覆盖它们循环的内容。这是练习和我不完整的解决方案：
编写一个JavaScript函数来参数化字符串。
grepl("^RT\\s+",c("RT hi","rt boo","rtlolo","im goodRT"), ignore.case=TRUE)
#[1] TRUE TRUE FALSE FALSE
grep("^RT\\s+", data$data, ignore.case=TRUE, value = TRUE)
#[1] "RT @4MySquad: This makes me sick!\\n#whiteprivilege\\n#BlackLivesMatter \\n#Policestate https:\\/\\/t.co\\/nDL0AHwWTd"
#[2] "RT @weaselzippers: D.C. Police Want Help Identifying #BlackLivesMatter Supporters Who Beat And Left Hero Marine For Dead\\u2026 https:\\/\\/t.co\\/tbmO\\u2026"
#[3] "RT @vicegandako: #PrayForMannyPacquiao #LoveWins"
#[4] "RT @eelawl1966: Former NAACP President Ben Jealous endorses Bernie Sanders\\n#BlackLivesMatter #BLM #Bernie2016 \\n https:\\/\\/t.co\\/Qom1KMwLHs"
#[5] "RT @JoshuaMannery: #BlackLivesMatter \\ud83d\\udc4a\\ud83c\\udffd https:\\/\\/t.co\\/tcEITKKGhd"
#[6] "RT @Uberarabic: \\u0644\\u0644\\u0639\\u0644\\u0645 \\u0639\\u0642\\u0648\\u0628\\u0629 \\u0627\\u0644\\u0645\\u062b\\u0644\\u064a\\u064a\\u0646 \\u0641\\u064a \\u062c\\u0645\\u064a\\u0639 \\u0627\\u0644\\u062f\\u0627\\u064a\\u0627\\u0646\\u0627\\u062a \\u0627\\u0644\\u0633\\u0645\\u0627\\u0648\\u064a\\u0629 \\u0647\\u064a \\u0627\\u0644\\u0642\\u062a\\u0644\\n\\n#LoveWins"
#[7] "RT @AishaYesufu: Let's not forget 219#ChibokGirls still in captivity today 676 days \\n#NeverToBeForgotten #CryingToBeRescued #BringBackOurGi\\u2026"
#[8] "RT @arctic_matters: Chukchi Sea. #LoveWins https:\\/\\/t.co\\/gH8KZgVZk3"
#[9] "RT @realkingcalii: #BlackLivesMatter Kendrick Lamar \\Alright\\ - https:\\/\\/t.co\\/amlRn0fKsA"
#[10] "RT @DreamersMOMS: Community representing #CCA & @geogroups making dirty $$$$ w\\/immigrants. #WeAreFlorida #not1more #immigration https:\\/\\/t.c\\u2026"
#[11] "RT @DreamersMOMS: Con compa\\u00f1eras de Carolina del Norte apoy\\u00e1ndonos en #Tallahassee. #ProteccionNoDeportation #Not1More @grisalonso https:\\/\\/\\u2026"
#[12] "RT @IkeIsaacson2: Hey #blacklivesmatter this is a hate crime done by racists in your name. https:\\/\\/t.co\\/6uGSXAJcrM"
答案应该是function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] === ".") {
joined_string[i] === "";
}
}
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));没有句点，但它会以句号robin-singh-from-usa形式出现。
答案 0 :(得分：1)
其他答案没有考虑到JavaScript中的字符串是不可变的。您无法更改字符串中的单个字符。你建立一个新的字符串。
在JavaScript中，字符串是不可变的。尝试更改字符串中的字符不起作用：
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] === ".") {
joined_string[i] = "";
}
}
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA.")); //This will not work:
您可以使用for循环构建新字符串，以便将.以外的每个字符单独添加到newString：
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
var newString = '';
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] !== ".") {
newString += joined_string[i];
} //We are replacing '.' with nothing, '', so no need for an else
}
return newString;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
但是，通常会使用Regular Expressions，特别是.replace()方法：
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var newString = lowercase_string.replace(/ /g,'-'); //Replace all spaces with '-'.
var newString = newString.replace(/\./g,''); //Replace all '.' with nothing. The '.'
// has to be quoted with \. as it
// has special meaning in a RegExp.
return newString;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
可以在一个声明中完成：
function string_parameterize(string) {
return string.toLowerCase().replace(/ /g,'-').replace(/\./g,'');
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
答案 1 :(得分：1)
您可以在输出中输入您不想要的每个字符[...]+。
var res = string.toLowerCase().replace(/[%\(\)\.\s]+/g, "-").replace(/-$/, "");
// ^ ^ ^ ^
// Here the characters you don't want to have in the output
+表示匹配一个 更多次。将匹配的字符替换为-。
然后使用-删除上一个-$。
总计
function string_parameterize(string) {
var res = string.toLowerCase().replace(/[%\(\)\.\s]+/g, "-").replace(/-$/, "");
return res;
}
console.log(string_parameterize("Это тест")); // A russian sentence
console.log(string_parameterize("Robin Singh%%() from USA. "));
console.log(string_parameterize("Robin ...Singh from USA....."));
console.log(string_parameterize("Robin Singh from USA "));
console.log(string_parameterize("Robin Singh from USA"));
Info关于正则表达式。
答案 2 :(得分：0)
function string_parameterize(str){
return str.toLowerCase().replace(".", "").split(" ").join("-");
}
console.log(string_parameterize("Robin Singh from USA."));
//will result in: robin-singh-from-usa
您的代码无效，因为在条件是您检查joined_string[i]==="."是否等于'.'且实际上它等于'USA.'。这就是为什么这个if条件从未遇到过并在最终结果中返回'.'的原因：
if (joined_string[i]===".") {
joined_string[i]==="";
}
答案 3 :(得分：0)
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
joined_string = joined_string.replace(".", "");
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
This is working in IE.
答案 4 :(得分：-2)
您正在检查 joined_string [i] 的值，而不是分配它。
joined_string[i] = "";
不
joined_string[i] === "";
答案 5 :(得分：-3)
Change:
if (joined_string[i]===".") {
joined_string[i]==="";
}
to
if (joined_string[i]===".") {
joined_string[i]="";
}