Cross-browser compatible flexbox implementation

_flexbox.scss

@mixin flex-container($dir: row nowrap, $align: stretch) {
    $ios_orient: horizontal;
    $ios_lines: multiple;

    @if nth($dir, 1) == column {
        $ios_orient: vertical;
    }
    @if length($dir) > 1 and nth($dir, 2) == nowrap {
        $ios_lines: single;
    }

    $ie10_dir: $dir;
    $ie10_wrap: none;
    @if length($dir) > 1 {
        $ie10_dir: nth($dir, 1);
        $ie10_wrap: nth($dir, 2);
    }

    display: -webkit-box; //ios
    display: -webkit-flex;
    display: -moz-flex;
    display: -ms-flexbox;
    display: flex;
    -webkit-flex-flow: $dir;
    -moz-flex-flow: $dir;
    -ms-flex-direction: $ie10_dir;
    -ms-flex-wrap: $ie10_wrap;
    -webkit-box-orient: $ios_orient; //ios
    -webkit-box-lines: $ios_lines; //ios
    flex-flow: $dir;
    -webkit-align-items: $align;
    -moz-align-items: $align;
    -ms-flex-align: $align;
    -webkit-box-align: $align; //ios
    align-items: $align;
}

@mixin justify($justify: flex-start) {
    $old: $justify;
    @if $justify == space-between {
        $old: justify;
    }
    @if $justify == flex-start {
        $old: start;
    }
    @if $justify == flex-end {
        $old: end;
    }
	flex-pack: $old;
	-ms-flex-pack: $old;
    -webkit-justify-content: $justify;
	justify-content: $justify;
}

@mixin flex-item($flex: 0 1 auto) {
    $ios_flex: nth($flex, 1);

    -webkit-box-flex: $ios_flex; //ios
    -webkit-flex: $flex;
    -moz-flex: $flex;
    -ms-flex: $flex;
    flex: $flex;
}