Parse string using javascript [closed]

You can find the pos of the "He " using the indexOf method and then get the position of the next line-break to remove that line using the substring method.

var someString = "Hello world,\n" +
    "He like cats and dogs\n" +
    "Bye bye";

var pos = someString.indexOf('He ');
var nextLineBreak = someString.indexOf('\n', pos);

var firstPart = someString.substring(0, pos);
var secondPart = someString.substring(nextLineBreak +1);

var finalString = firstPart + secondPart;
alert(finalString);

jsFiddle here : http://jsfiddle.net/zw2Gh/

Here is a single line regex based replace:

someString.replace(/^He .*(\n|$)/mg, '');

It enables the multiline and global flags (mg) which allows us to use ^ and $ to match after and before newlines. And it also will remove all occurrences of the pattern. If you want lines with just "He\n" to be replaced, you will need to make the ' .*' optional, like so:

someString.replace(/^He( .*)?(\n|$)/mg, '');

You can split the string up into separate lines, throw away the lines you want, and finally join the lines back into one string:

var string = "test\nHe test\ntest"; // "\n" represents a newline

var result = string.split("\n") // split into lines
                   .filter(function(line) {              // only retain lines
                       return line.indexOf("He ") !== 0; // that don't start
                   })                                    // with "He " *
                   .join("\n"); // join the lines back into one string

*) "Doesn't start" means: the characters are not apperant at index 0 in the line.