Add helper functions to get_text() between 2 markers and del_chars() [done]

[kensoh]

This is very useful when extracting text from a chunk of text content, by providing the left anchor and right anchor.

aisingapore/TagUI#972 (comment)

// retrieve text between 2 provided anchors in given text content
function get_text(source_text, left_marker, right_marker, optional_count) {
    if (!source_text || !left_marker || !right_marker) return '';
    var left_position = source_text.indexOf(left_marker); if (left_position == -1) return '';
    var right_position = source_text.indexOf(right_marker, left_position+1); if (right_position == -1) return '';
    if (optional_count > 1) {var occurrence_count = 2; while(occurrence_count <= optional_count) {occurrence_count++;
        left_position = source_text.indexOf(left_marker, right_position+1); if (left_position == -1) return '';
        right_position = source_text.indexOf(right_marker, left_position+1); if (right_position == -1) return '';}}
    return source_text.slice(left_position + left_marker.length, right_position).trim();}

[kensoh]

Consider also adding del_chars() from upstream - good to have that for data-cleaning

// return given string after deleting all occurrences of given characters
function del_chars(source_text, characters) {
    if (!source_text) return ''; else if (!characters) return source_text;
    characters = characters.replace(/\\n/g,'\n').replace(/\\r/g,'\r').replace(/\\t/g,'\t');
    characters = characters.replace(/\\f/g,'\f').replace(/\\v/g,'\v').replace(/\\\\/g,'\\');
    for (char_counter = 0; char_counter < characters.length; char_counter++) {
        if (characters[char_counter] != '\\')
            source_text = source_text.replace(new RegExp(characters[char_counter],'g'),'');
        else
            source_text = source_text.replace(/\\/g,'');}
    return source_text;}

[kensoh]

After thinking through, better to create the functions within the package instead of routing to TagUI's functions

[kensoh]

del_chars() is something as trivial as below in Python (but a loop is required if multiple characters needed) -

text_content.replace('\r', '')

[kensoh]

get_text() is something as trivial as below in Python (but probably can't handle many negative edge cases) -

text_content.split(left_marker)[1].split(right_marker)[0]