用一个值替换第一次出现，用另一个值替换第二次

Question

Giving this original string...

Test text _with bold_ and perhaps one another text _with bold in the same string_.

... how to efficiently replace the first occurrence of " _ " with "< b >" and the second occurrence " _ " with "< /b >" to achieve the following result:

Test text <b>with bold</b> and perhaps one more text <b>with bold in the same string</b>.

Note: I have an array of hundreds of those strings that will need to go through this process in order to render in the page.

Answer 1

You can use regex for this.

The replace-pattern is the following:

_(.*?)_ with the flag g at the end - so it will replace until all occurances are satisfied.

The ? in the regex says it will stop matching at the first _ afert the opening _ (non-greedy).

<b>$1</b> says replace the matched string with this. Where the $1 refers to the content matched in the brackets ()

 var text = "This is _bold text_ and here _some more_"; var text_replaced = text.replace(/_(.*?)_/g, '<b>$1</b>'); document.getElementById('result').innerHTML = text_replaced;

 <span id="result" />

Answer 2

You can run a while loop which checks if there any more underscores in the text and replaces them, assuming that there must be an even number of "_" in the text:

var test = "text _with bold_ and perhaps one another text _with bold in the same string_.";
b_index = test.indexOf("_");

while (b_index != -1) {
  test = test.replace("_", "<b>");
  test = test.replace("_",  "</b>");
  b_index = test.indexOf("_");
}

After the while loop, you can assign the innerHTML of whichever element you wish to the variable test.