How to select line of text in textarea

Question

I have a textarea that is used to hold massive SQL scripts for parsing. When the user clicks the "Parse" button, they get summary information on the SQL script.

I'd like the summary information to be clickable so that when it's clicked, the line of the SQL script is highlighted in the textarea.

I already have the line number in the output so all I need is the javascript or jquery that tells it which line of the textarea to highlight.

Is there some type of "goToLine" function? In all my searching, nothing quite addresses what I'm looking for.

Solution 1

This function expects first parameter to be reference to your textarea and second parameter to be the line number

function selectTextareaLine(tarea,lineNum) {
    lineNum--; // array starts at 0
    var lines = tarea.value.split("\n");

    // calculate start/end
    var startPos = 0, endPos = tarea.value.length;
    for(var x = 0; x < lines.length; x++) {
        if(x == lineNum) {
            break;
        }
        startPos += (lines[x].length+1);

    }

    var endPos = lines[lineNum].length+startPos;

    // do selection
    // Chrome / Firefox

    if(typeof(tarea.selectionStart) != "undefined") {
        tarea.focus();
        tarea.selectionStart = startPos;
        tarea.selectionEnd = endPos;
        return true;
    }

    // IE
    if (document.selection && document.selection.createRange) {
        tarea.focus();
        tarea.select();
        var range = document.selection.createRange();
        range.collapse(true);
        range.moveEnd("character", endPos);
        range.moveStart("character", startPos);
        range.select();
        return true;
    }

    return false;
}

Usage:

 var tarea = document.getElementById('myTextarea');
 selectTextareaLine(tarea,3); // selects line 3

Working example:

http://jsfiddle.net/5enfp/

Solution 2

The code in the post by darkheir does not work correctly. Based on it I shortened the code and made it working.

    function onClickSelection(textarea){
        if(typeof textarea.selectionStart=='undefined'){
            return false;
        }
        var startPos=(textarea.value.substring(0,textarea.selectionStart).lastIndexOf("\n")>=0)?textarea.value.substring(0,textarea.selectionStart).lastIndexOf("\n"):0;
        var endPos=(textarea.value.substring(textarea.selectionEnd,textarea.value.length).indexOf("\n")>=0)?textarea.selectionEnd+textarea.value.substring(textarea.selectionEnd,textarea.value.length).indexOf("\n"):textarea.value.length;
        textarea.selectionStart=startPos;
        textarea.selectionEnd=endPos;
        return true; 
    }

Solution 3

A somewhat neater version of the search for lines:

    function select_textarea_line (ta, line_index) {

        const newlines = [-1];   // Index of imaginary \n before first line
        for (let i = 0; i < ta.value.length; ++i) {
            if (ta.value[i] == '\n') newlines.push( i );
        }

        ta.focus();
        ta.selectionStart = newlines[line_index] + 1;
        ta.selectionEnd   = newlines[line_index + 1];

    } // select_textarea_line

Comments

[Flat Cat]

That is spectacularly fantastic. Thank you so much!

[Gabriel]

your startPos selected also the \n character from previous line, adding +1 to it fixed the job (textarea.value.substring(0, textarea.selectionStart).lastIndexOf("\n") >= 0) ? textarea.value.substring(0, textarea.selectionStart).lastIndexOf("\n") + 1 : 0;

[Roy Prins]

If for some reason you find yourself needing to deselect any selection: window.getSelection().removeAllRanges()

[Amr Elgarhy]

I have no idea why but the jsfiddle is not selecting the line text, it is not working.

[Himanshu Tanwar]

@AmrElgarhy, It wasn't working for me as well, I removed mootools and it started to work. If you can't remove mootools then replace it with jquery.

[Amr Elgarhy]

@HimanshuTanwar Yes, I added jquery instead of mootools and it worked, thank you.

[Albert F D]

Hello... sorry for reviving this thread. As a complete novice to JS I adapted it to work in an HTA using the onclick event for the textarea element. However it appears to work perfectly well without the if condition, and return statements, under what circumstances are they required?

[Fadi]

@lostsorce how we can change the background colour of the selected text?